secondary batteries

Abstract

This secondary battery 100 comprises: a positive electrode 101 containing cystine; a negative electrode 103 containing magnesium, sodium, or calcium; and an electrolyte 102 disposed between the positive electrode 101 and the negative electrode 103.

Description

[Technical Field]

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

[0002] Traditionally, secondary batteries such as lead-acid batteries, lithium-ion secondary batteries, lithium-ion polymer secondary batteries, nickel-metal hydride batteries, or nickel-cadmium batteries have been widely used in small devices, sensors, mobile equipment, etc. In addition, with the recent development of the Internet of Things (IoT), development is also progressing for scattered sensors that can be installed throughout nature, such as in soil or forests.

[0003] Furthermore, air batteries with low environmental impact are being investigated (Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6711915 Summary of the Invention [Problem to be solved by the invention]

[0005] Conventional batteries contain materials with a high environmental impact, such as lead compounds, cadmium compounds, manganese compounds, nickel compounds, or fluorine compounds, and require specific disposal procedures. Therefore, conventional batteries are not suitable for disposal as general waste or for use in scattered sensors. Therefore, there is a demand for batteries made entirely of materials with a low environmental impact.

[0006] The battery principle of Patent Document 1 is an air battery, which uses oxygen in the air as the positive electrode active material, so the battery must have an air intake. As a result, air batteries have the disadvantage that the electrolyte evaporates from the air intake, making them unsuitable for long-term use. Therefore, there is a need for a new, environmentally friendly battery that does not require oxygen as the positive electrode active material.

[0007] Secondary batteries can be charged and discharged repeatedly, which means they can be disposed of less than primary batteries with the same capacity and voltage, and they have a lower environmental impact.

[0008] The present invention has been made in view of the above circumstances, and has an object to provide a secondary battery that has a low environmental impact and can be used for a long period of time. [Means for solving the problem]

[0009] A secondary battery according to one aspect of the present invention includes a positive electrode containing cystine, a negative electrode containing magnesium, sodium, or calcium, and an electrolyte disposed between the positive electrode and the negative electrode. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a secondary battery that has a low environmental impact and can be used for a long period of time. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram of the secondary battery of this embodiment. [Figure 2] FIG. 2 is a schematic cross-sectional view showing the structure of a coin-type secondary battery. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0013] [Secondary battery configuration] FIG. 1 is a diagram showing the configuration of a secondary battery 100 according to an embodiment of the present invention. The secondary battery 100 includes a positive electrode 101 containing cystine, a negative electrode 103 containing magnesium, sodium, or calcium, and an electrolyte 102 disposed between the positive electrode 101 and the negative electrode 103. A non-aqueous electrolyte solution is preferably used for the electrolyte 102. In the embodiment described below, a case where magnesium is used for the negative electrode 103 and a non-aqueous electrolyte solution is used for the electrolyte 102 will be described as an example, but the present invention is not limited to this.

[0014] The charge / discharge reaction in the negative electrode 103 is shown in formula (1), and the charge / discharge reaction in the positive electrode 101 is shown in formula (2).

[0015] [ka]

[0016] [ka]

[0017] The disulfide bond of cystine contained in the positive electrode 101 is cleaved by electrochemical reduction during discharge and is regenerated by electrochemical oxidation during charge.

[0018] During discharge, electrochemical oxidation occurs at the negative electrode 103 as shown in formula (1). Magnesium is converted into magnesium ions (Mg + ) and electrons. Meanwhile, electrochemical reduction occurs at the positive electrode 101. The disulfide bond of cystine is cleaved and reacts with the released magnesium ions and electrons at the negative electrode 103 to produce magnesium salts.

[0019] During charging, the reaction proceeds in the reverse direction: electrochemical oxidation occurs at the positive electrode 101, converting the magnesium salt back to cystine, and electrochemical reduction occurs at the negative electrode 103, converting the magnesium ions back to magnesium.

[0020] The cystine contained in the positive electrode 101 may be in a polymerized state. An example of the polymerized cystine is a polymer represented by the formula (3).

[0021] [ka]

[0022] The positive electrode 101 contains a polymer containing a repeating unit represented by formula (4) as the polymerized cystine represented by formula (3).

[0023] [ka]

[0024] When a polymer compound is used as the active material contained in the positive electrode 101, the active material is unlikely to dissolve in the electrolyte 102 due to an electrochemical reaction. The positive electrode 101 is expected to have excellent stability with little deterioration over a long period of time. The molecular weight of the cystine polymer compound is preferably 10,000 or more, and more preferably 100,000 or more.

[0025] Furthermore, when cystine is used as the positive electrode active material and Mg is used as the negative electrode active material, the theoretical electromotive force is approximately 2.5 V. When cystine is used as the positive electrode active material and Na or Ca is used as the negative electrode active material, the theoretical electromotive force is approximately 3.0 V.

[0026] The secondary battery 100 of this embodiment is expected to be an environmentally friendly battery by using cystine as the positive electrode active material, magnesium, sodium, or calcium as the negative electrode active material, and a non-aqueous electrolyte solution containing no fluorine compounds. The positive electrode 101 can contain a positive electrode active material and a conductive additive as components, and the negative electrode 103 can contain a negative electrode active material and a conductive additive as components.

[0027] Each of the above components will be described below.

[0028] (1) Positive electrode The positive electrode 101 contains at least cystine, which is a positive electrode active material, and may contain a current collector as needed. The positive electrode 101 is preferably formed on a porous material containing at least one selected from the group consisting of aluminum, copper, and iron, or on a nonwoven current collector containing carbon. Alternatively, the positive electrode 101 may be formed as a bicontinuous body in which a plurality of integrated nanostructures have branches, forming a three-dimensional network structure.

[0029] In this embodiment, the positive electrode 101 is preferably formed without a binder. In conventional positive electrode fabrication methods, a binder is used to stabilize the positive electrode structure (ensuring discharge stability), but the binder has the disadvantage of increasing internal resistance. In contrast, in the positive electrode 101 of the embodiment, cystine is directly supported on a network structure such as a nonwoven current collector or a co-continuous body, making it possible to stabilize the positive electrode structure without using a binder. This is expected to reduce the internal resistance of the battery compared to conventional fabrication methods that use a binder.

[0030] As described above, the positive electrode 101 containing cystine as a positive electrode active material can achieve high activity in charge and discharge reactions. Furthermore, the positive electrode 101 of the secondary battery configured as described above can fully utilize the potential of cystine as a positive electrode active material.

[0031] (1-1) Positive electrode active material The positive electrode active material of this embodiment contains at least cystine, which is derived from a living organism and therefore has a low environmental impact, and is also inexpensive.

[0032] The positive electrode active material is preferably in a polymer state because a small molecular weight of the positive electrode active material dissolves easily in the electrolyte. The molecular weight of the positive electrode active material is preferably 10,000 or more, and more preferably 100,000 or more.

[0033] Cystine can be obtained, for example, as a commercial product or by known synthesis, and polymeric compounds of cystine can be obtained by known synthesis.

[0034] (1-2) Preparation of positive electrode using conductive additive In another embodiment, the positive electrode 101 containing cystine may contain a conductive additive and a binder. Examples of the conductive additive include carbon. Specific examples of the conductive additive include carbon blacks such as ketjen black and acetylene black, activated carbon, graphite, and carbon fibers. To ensure sufficient reaction sites within the positive electrode 101, carbon with small particles is preferred. Specifically, a particle diameter of 1 μm or less is desirable. These carbons can be obtained, for example, as commercial products or by known synthesis. Specific examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene butadiene rubber, ethylene propylene diene rubber, and natural rubber.

[0035] In this way, in another embodiment, in addition to the positive electrode active material, cystine powder, a conductive additive and a binder may be mixed, and the mixture may be joined with a conductive material, as in the conventional positive electrode production method, to prepare the positive electrode 101.

[0036] (1-3) Preparation of positive electrode using current collector In this embodiment, a porous body containing at least one selected from the group consisting of aluminum, copper, and iron, or a nonwoven fabric current collector containing carbon may directly support the positive electrode active material. The porous body or nonwoven fabric current collector is available, for example, as a commercially available product.

[0037] A three-dimensional network structured cocontinuum in which multiple nanostructures are integrated by non-covalent bonds may directly support a positive electrode active material without using a binder. Here, the cocontinuum has a deformable bond between the nanostructures, resulting in a stretchable, integrated structure. The cocontinuum preferably has an average pore size of 0.1 to 50 μm. The nanostructure is a nanosheet or nanofiber and is electrically conductive. Examples of such nanosheets include graphene. Examples of nanofibers include iron oxide, manganese oxide, silicon, or carbonized cellulose. Nanofibers are fibrous materials with a diameter of 1 nm to 1 μm and a length 100 times or more their diameter. Carbonized cellulose can be produced by heating and carbonizing a gel in which cellulose nanofibers are dispersed in an inert gas atmosphere.

[0038] A co-continuous body can be produced by freezing a sol or gel in which nanostructures such as nanosheets or nanofibers are dispersed, and then drying the resulting frozen body in a vacuum. The dispersion medium for the sol is, specifically, an aqueous system such as water, or an organic system such as carboxylic acid, methanol, ethanol, propanol, n-butanol, isobutanol, n-butylamine, dodecane, unsaturated fatty acid, ethylene glycol, heptane, hexadecane, isoamyl alcohol, octanol, isopropanol, acetone, or glycerin. The dispersion medium for the sol may be a mixture of two or more of these organic systems. Specifically, the dispersion medium for the gel is an aqueous system such as water (HO), or an organic system such as carboxylic acid, methanol (CHOH), ethanol (CHO), propanol (CHO), n-butanol, isobutanol, n-butylamine, dodecane, unsaturated fatty acid, ethylene glycol, heptane, hexadecane, isoamyl alcohol, octanol, isopropanol, acetone, or glycerin. The dispersion medium for the gel may be a mixture of two or more types selected from these aqueous and organic systems.

[0039] The degree of vacuum in the drying process varies depending on the dispersion medium used, but there are no particular restrictions as long as it is a degree of vacuum that allows the dispersion medium to sublimate. For example, when water is used as the dispersion medium, a vacuum of 0.06 MPa or less is required, but drying takes time because heat is lost as latent heat of sublimation. For this reason, the degree of vacuum should be 1.0 x 10 ―6 to 1.0×10 ―2 Pa is preferred. Furthermore, heat may be applied using a heater or the like during drying. This co-continuum can have a larger specific surface area than commercially available conductive porous bodies or nonwoven fabric current collectors. The specific surface area of ​​this co-continuum is 200 m 2 / g or more is preferable.

[0040] Methods for supporting the positive electrode active material on the porous or nonwoven current collector or co-continuous body include physical methods such as vapor deposition, sputtering, and planetary ball milling; methods in which the porous or nonwoven current collector or co-continuous body is immersed in a liquid containing the positive electrode active material and then dried; chemical methods such as the sol-gel method; and known methods. To form a simple, high-quality positive electrode 101, a preferred method involves immersing the porous or nonwoven current collector or co-continuous body in a liquid containing the positive electrode active material and then drying the co-continuous body immersed in the liquid containing the positive electrode active material to support the positive electrode active material. Here, cold pressing or hot pressing the dried electrode can be used to increase the electrode strength and produce a more stable positive electrode 101. The solvent for dissolving the positive electrode active material is specifically an aqueous solvent such as water, or an organic solvent such as tetrahydrofuran (THF), tetrahydrofuran (THP), dioxane, diethyl ether, N-methyl-2-pyrrolidone (NMP), hexamethylphosphoramide (HMPA), tetramethylurea (TMU), dimethylacetamide (DMAc), dimethylformaldehyde (DMF), dimethyl sulfoxide (DMSO), m-cresol, or chloroform. Two or more types of solvents selected from these aqueous or organic solvents may be mixed.

[0041] In the secondary battery 100 of this embodiment, the reaction represented by formula (2) proceeds on the surface of the positive electrode 101, so it is preferable to generate a large number of reaction sites inside the positive electrode 101. In the case of conventional positive electrodes formed using the aforementioned conductive additives and binders, when the specific surface area is increased, the binding strength between the conductive additives decreases, causing structural deterioration, making stable discharge difficult and reducing the discharge capacity. In contrast, the positive electrode 101 formed using the aforementioned porous or nonwoven fabric current collector or co-continuum ensures a large number of reaction sites and solves the conventional problems described above, thereby enabling a high discharge capacity. In particular, the co-continuum has a high bulk density and can support a larger amount of positive electrode active material, thereby improving the efficiency of the battery.

[0042] As described above, by fabricating a positive electrode containing cystine as a positive electrode active material, it is possible to obtain a positive electrode 101 that is highly active in charge and discharge reactions. Furthermore, by fabricating the positive electrode 101 of the secondary battery 100 configured as described above, it is possible to fully utilize the potential of cystine as a positive electrode active material.

[0043] (2) Negative electrode The secondary battery 100 of this embodiment contains at least magnesium (Mg), sodium (Na), or calcium (Ca) as the negative electrode active material. This negative electrode active material may contain magnesium (Mg), sodium (Na), or calcium (Ca) as a main component. The negative electrode active material may be an alloy containing at least one component selected from the group consisting of lithium (Li), zinc (Zn), aluminum (Al), iron (Fe), tin (Sn), and carbon (C) in addition to magnesium (Mg), sodium (Na), or calcium (Ca).

[0044] (3) Electrolyte The secondary battery 100 of this embodiment contains a non-aqueous electrolyte solution as the electrolyte 102. This non-aqueous electrolyte solution contains magnesium ions (Mg 2+ ), sodium ions (Na + ) or calcium ions (Ca 2+) is a solution containing an electrolyte capable of transferring. The non-aqueous electrolyte solution uses an organic solvent as the main solvent and may contain, for example, water in addition to the organic solvent. The non-aqueous electrolyte solution may be an electrolyte solution in which a magnesium salt, a sodium salt, or a calcium salt is dissolved in an organic solvent. The organic solvent may be at least one selected from the group consisting of carbonate ester solvents such as dimethyl carbonate (DMC), methyl ethyl carbonate (MEC), methyl propyl carbonate (MPC), methyl isopropyl carbonate (MIPC), methyl butyl carbonate (MBC), diethyl carbonate (DEC), ethyl propyl carbonate (EPC), ethyl isopropyl carbonate (EIPC), ethyl butyl carbonate (EBC), dipropyl carbonate (DPC), diisopropyl carbonate (DIPC), dibutyl carbonate (DBC), ethylene carbonate (EC), propylene carbonate (PC), and 1,2-butylene carbonate (1,2-BC); ether solvents such as 1,2-dimethoxyethane (DME) and tetraethylene glycol dimethyl ether (TEGDME); lactone solvents such as γ-butyrotactone (GBL); and sulfoxide solvents such as dimethyl sulfoxide (DMSO). Magnesium salts, sodium salts, and calcium salts are represented by Mg-X2, Na-X2, and Ca-X2, respectively. where X is, for example, Cl, Br, I, BF4, PF6, CF3SO3, ClO4, CF3CO2, AsF6, SbF6, AlCl4, N(CF3SO2)2, N(CF3CF2SO2)2, PF3(C2F5)3, N(FSO2)2, N(FSO2)(CF3SO2), N(CF3CF2SO2)2, N(C2F4S2O4), N(C3F6S2O4), N(CN)2, N(CF3SO2)(CF3CO) or R 1 FBF3 (However, R 1 F=nC m F 2m+1 , m = a natural number from 1 to 4) and R 2 BF3 (However, R 2 =nC p H 2p+1 (where p is a natural number from 1 to 5). X is preferably Cl, Br, I, ClO4, AlCl, or N(CN)2, which is not a fluorine compound, from the viewpoint of environmental load. Furthermore, X may be a metal salt obtained by mixing two or more of these.

[0045] In this embodiment, a non-aqueous electrolytic solution is used as the electrolyte 102, but a solid electrolyte such as a gel or solid may also be used. That is, the electrolyte 102 may be in any form such as a liquid, cream, gel, or solid.

[0046] (4) Other factors In addition to the above components, the secondary battery 100 of this embodiment can include structural members such as a separator and a battery case, as well as other elements required for a secondary battery. These other elements can be conventionally known, but from the perspective of environmental impact and waste disposal, they preferably do not contain hazardous substances, precious metals, etc. Furthermore, it is more preferable that these other elements be made of biologically derived, biodegradable materials.

[0047] (5) Secondary battery manufacturing method As described above, the secondary battery 100 of this embodiment includes at least a positive electrode 101, a negative electrode 103, and an electrolyte 102. As illustrated in Fig. 1, the electrolyte 102 is disposed between the positive electrode 101 and the negative electrode 103 so as to be in contact with the positive electrode 101 and the negative electrode 103. The secondary battery 100 having such a configuration can be prepared in the same manner as a conventional secondary battery.

[0048] For example, the secondary battery 100 may be produced by assembling, according to conventional techniques, each of the elements: a positive electrode 101 containing a positive electrode active material containing cystine as described above, a negative electrode 103 containing magnesium (Mg), sodium (Na) or calcium (Ca), and an electrolyte 102 disposed so as to be in contact with the positive electrode 101 and the negative electrode 103. The positive electrode 101 may contain a conductive additive and a binder.

[0049] As an embodiment of the method for manufacturing the secondary battery 100, for example, a coin-type secondary battery can be manufactured.

[0050] 2 is a schematic cross-sectional view showing the structure of a coin-type secondary battery 100a. Specifically, first, the positive electrode 101 is placed in a circular positive electrode case 201. A separator (not shown) is placed on the positive electrode 101, and a non-aqueous electrolyte solution is poured into the placed separator as the electrolyte 102. A propylene gasket 203 is fitted around the outer periphery of a circular negative electrode case 202. Next, the negative electrode 103 is placed on the electrolyte 102, and the negative electrode case 202 with the propylene gasket 203 fitted thereto is placed over the positive electrode case 201. At this time, the propylene gasket 203 abuts against the inner edge of the positive electrode case 201, and the negative electrode case 202 is placed over the positive electrode case 201 so that the positive electrode 101 and the negative electrode 103 do not come into contact with each other. Next, the peripheral edges of the positive electrode case 201 and the negative electrode case 202 are crimped using a coin cell crimping machine, whereby the coin-type secondary battery 100a including the propylene gasket 203 can be produced.

[0051] The illustrated coin-type secondary battery 100a uses cystine as the positive electrode active material. Therefore, unlike air batteries that use oxygen in the air as the positive electrode active material, the positive electrode case 201 of this embodiment does not need to be provided with an air intake port. In other words, this embodiment can produce a sealed battery. Therefore, the coin-type secondary battery 100a of this embodiment can be stored for a long period of time without the electrolyte volatilizing through the air intake port.

[0052] [Example] Examples of the secondary battery 100 according to this embodiment will be described in detail below. The secondary battery 100 used in each example uses magnesium (Mg), sodium (Na), and calcium (Ca) in the negative electrode 103. The secondary battery 100 using magnesium (Mg), sodium (Na), and calcium (Ca) in the negative electrode 103 uses a propylene carbonate solution containing Mg(ClO4)2, NaClO4, and Ca(ClO4)2 as the electrolyte 102. Note that the present invention is not limited to the examples shown below and can be practiced with appropriate modifications.

[0053] <First Example> In the first example, a coin-type secondary battery 100a shown in FIG. 2 was fabricated by the following procedure. Cystine was used as the positive electrode active material. Magnesium (Mg) foil, sodium (Na) foil, and calcium (Ca) foil were used as the negative electrode active materials. For the coin-type secondary battery 100a using magnesium (Mg) foil, sodium (Na) foil, and calcium (Ca) foil, respectively, a propylene carbonate solution containing 0.5 mol / L of Mg(ClO4)2, NaClO4, and Ca(ClO4)2 was used as the electrolyte 102.

[0054] (Preparation of Positive Electrode 101) Cystine powder (Tokyo Chemical Industry Co., Ltd.), Ketjenblack powder (EC600JD, Lion Specialty Chemicals), and polytetrafluoroethylene (PTFE) powder were thoroughly crushed and mixed in a weight ratio of 80:10:10 using a grinder, and then roll-formed to prepare a sheet electrode (thickness: 0.5 mm). This sheet electrode was cut into a circle with a diameter of 16 mm and pressed onto a copper mesh to obtain the positive electrode 101.

[0055] (Preparation of Negative Electrode 103) Magnesium (Mg) foil (thickness 150 μm, Nilaco Corporation), sodium (Na) foil (thickness 150 μm, Sigma-Aldrich Co. LLC), and calcium (Ca) foil (thickness 150 μm, Nilaco Corporation) were each cut into a circle with a diameter of 16 mm, and each of these was bonded to copper foil (Nilaco Corporation) using an ultrasonic welding machine to obtain negative electrode 103.

[0056] (Preparation of secondary battery 100) A coin-type secondary battery 100a shown in FIG. 2 was fabricated using a coin battery case (Hosensha).

[0057] A cellulose-based separator (Nippon Kodoshi Kogyo Co., Ltd.) cut to a diameter of 18 mm was placed on the positive electrode case 201 containing the positive electrode 101 prepared by the above method, and a propylene carbonate solution (Kishida Chemical Co., Ltd.) containing Mg(ClO4)2, NaClO4, and Ca(ClO4)2 was poured into the placed separator as the electrolyte 102. The negative electrode 103 was placed on the electrolyte 102, and the negative electrode case 202 was placed over the positive electrode case 201. The peripheral portions of the positive electrode case 201 and the negative electrode case 202 were crimped using a coin cell crimping machine, thereby obtaining a coin-type secondary battery 100a including a propylene gasket 203.

[0058] (Battery performance) The battery performance of the secondary battery 100 prepared by the above procedure was measured. The battery cycle test was carried out using a charge / discharge measurement system (manufactured by Bio Logic) at a current density of 1.0 mA / cm per effective area of ​​the positive electrode 101. 2 A current was applied, and the discharge voltage was measured until the battery voltage dropped from the open circuit voltage to 0.10 V. The battery discharge test was carried out under normal living conditions. The discharge capacity was expressed as the value per unit weight of the positive electrode active material (cystine) (mAh / g).

[0059] The discharge capacity and discharge voltage of the secondary battery of the first example are shown in Table 1. As shown in Table 1, the discharge voltages of the batteries of the first example using magnesium (Mg), sodium (Na), and calcium (Ca) in the negative electrode 103 were 0.5 V, 1.0 V, and 1.1 V, respectively, and the discharge capacities were 82 mAh / g, 142 mAh / g, and 101 mAh / g, respectively. Here, the discharge voltage is defined as the discharge voltage at half the total discharge capacity. As such, it was found that the secondary battery of the first example had excellent battery performance.

[0060] [Table 1]

[0061] <Second Example> In the second example, a coin-type secondary battery 100a shown in FIG. 2 was fabricated by the following procedure. Cystine was used as the positive electrode active material, and the positive electrode active material was supported on a nonwoven current collector (carbon felt) containing carbon. Magnesium (Mg) foil, sodium (Na) foil, and calcium (Ca) foil were used as the negative electrode active materials. For the coin-type secondary battery 100a using magnesium (Mg) foil, sodium (Na) foil, and calcium (Ca) foil, a propylene carbonate solution containing 0.5 mol / L of Mg(ClO4)2, NaClO4, and Ca(ClO4)2 was used as the electrolyte 102.

[0062] The battery was evaluated in the same manner as in the first example.

[0063] (Preparation of Positive Electrode 101) Carbon felt (Toyobo Co., Ltd.) was immersed in a solution prepared by dissolving cystine powder (Tokyo Chemical Industry Co., Ltd.) in 1.0 M hydrochloric acid (Tokyo Chemical Industry Co., Ltd.). The carbon felt was dried in a vacuum dryer at 80°C for 30 minutes to precipitate cystine on the carbon felt, which was then washed with pure water. The cystine-containing carbon felt was then cut into a circle with a diameter of 16 mm to obtain a positive electrode 101.

[0064] (Preparation of Negative Electrode 103) Magnesium (Mg) foil (thickness 150 μm, Nilaco Corporation), sodium (Na) foil (thickness 150 μm, Sigma-Aldrich Co. LLC), and calcium (Ca) foil (thickness 150 μm, Nilaco Corporation) were each cut into a circle with a diameter of 16 mm, and each of these was bonded to copper foil (Nilaco Corporation) using an ultrasonic welding machine to obtain negative electrode 103.

[0065] (Preparation of secondary battery 100) A coin-type secondary battery 100a shown in FIG. 2 was fabricated using a coin battery case (Hosensha).

[0066] A cellulose-based separator (Nippon Kodoshi Kogyo Co., Ltd.) cut to a diameter of 18 mm was placed on the positive electrode case 201 containing the positive electrode 101 prepared by the above method, and a propylene carbonate solution (Kishida Chemical Co., Ltd.) containing Mg(ClO4)2, NaClO4, and Ca(ClO4)2 was poured into the placed separator as the electrolyte 102. The negative electrode 103 was placed on the electrolyte 102, and the negative electrode case 202 was placed over the positive electrode case 201. The peripheral portions of the positive electrode case 201 and the negative electrode case 202 were crimped using a coin cell crimping machine, thereby obtaining a coin-type secondary battery 100a including a propylene gasket 203.

[0067] (Battery performance) The discharge capacity and discharge voltage of the secondary battery of the second example are shown in Table 1. As shown in Table 1, the discharge capacity of the battery of the second example using magnesium (Mg) for the negative electrode 103 was 124 mAh / g, which was a larger value than that of the first example. The discharge capacities of the batteries using sodium (Na) and calcium (Ca) for the negative electrodes were also larger than that of the first example.

[0068] Furthermore, as shown in Table 1, the discharge voltage of the second example is higher than that of the first example. That is, the second example exhibits a greater reduction in overvoltage than the first example, and an improvement in discharge energy efficiency was achieved.

[0069] These improvements in characteristics are believed to be due to the use of positive electrode 101 formed by bonding a positive electrode active material to carbon felt, which reduced the internal resistance of the battery and allowed the battery reaction to proceed more efficiently.

[0070] <Third Example> In the third example, a coin-type secondary battery 100a shown in FIG. 2 was fabricated by the following procedure. Cystine was used as the positive electrode active material and supported on a co-continuum. Magnesium (Mg) foil, sodium (Na) foil, and calcium (Ca) foil were used as the negative electrode active materials. For the coin-type secondary battery 100a using magnesium (Mg) foil, sodium (Na) foil, and calcium (Ca) foil, a propylene carbonate solution containing 0.5 mol / L of Mg(ClO4)2, NaClO4, and Ca(ClO4)2 was used as the electrolyte 102.

[0071] The battery evaluation method was the same as in the first and second examples.

[0072] (Preparation of Positive Electrode 101) The co-continuum was immersed in a solution prepared by dissolving cystine powder (Tokyo Chemical Industry Co., Ltd.) in 1.0 M hydrochloric acid (Tokyo Chemical Industry Co., Ltd.). The co-continuum was dried in a vacuum dryer at 80°C for 30 minutes to precipitate cystine in the co-continuum, which was then washed with pure water. The cystine-containing co-continuum was then cut into a circle with a diameter of 16 mm to obtain a positive electrode 101.

[0073] To produce the co-continuum, first, bacterial cellulose gel produced by the acetic acid bacterium Acetobacter xylinum was placed in a test tube and immersed in liquid nitrogen for 30 minutes to completely freeze the bacterial cellulose gel. Next, the frozen bacterial cellulose gel was placed in an eggplant flask and dried in a freeze dryer (Tokyo Rikakikai Co., Ltd.) under a vacuum of less than 10 Pa. The gel was then carbonized by firing at 1200°C for 2 hours in a nitrogen atmosphere to produce a co-continuum.

[0074] (Preparation of Negative Electrode 103) Magnesium (Mg) foil (thickness 150 μm, Nilaco Corporation), sodium (Na) foil (thickness 150 μm, Sigma-Aldrich Co. LLC), and calcium (Ca) foil (thickness 150 μm, Nilaco Corporation) were each cut into a circle with a diameter of 16 mm, and each of these was bonded to copper foil (Nilaco Corporation) using an ultrasonic welding machine to obtain negative electrode 103.

[0075] (Preparation of secondary battery 100) A coin-type secondary battery 100a shown in FIG. 2 was fabricated using a coin battery case (Hosensha).

[0076] A cellulose-based separator (Nippon Kodoshi Kogyo Co., Ltd.) cut to a diameter of 18 mm was placed on a positive electrode case 201 containing the positive electrode 101 prepared by the above method, and a propylene carbonate solution (Kishida Chemical Co., Ltd.) containing Mg(ClO4)2, NaClO4, and Ca(ClO4)2 was poured into the placed separator as electrolyte 102. The negative electrode 103 was placed on the electrolyte 102, and the negative electrode case 202 was placed over the positive electrode case 201. The peripheral portions of the positive electrode case 201 and the negative electrode case 202 were crimped using a coin cell crimping machine, thereby obtaining a coin-type secondary battery 100a including a propylene gasket 203.

[0077] (Battery performance) The discharge capacity and discharge voltage of the secondary battery of the third example are shown in Table 1. As shown in Table 1, the discharge capacity of the battery of the third example using magnesium (Mg) for the negative electrode 103 was 162 mAh / g, which was a value larger than those of the first example and the second example. The discharge capacities of the batteries using sodium (Na) and calcium (Ca) for the negative electrode 103, respectively, were also larger than those of the first example and the second example.

[0078] Furthermore, as shown in Table 1, the discharge voltage of the third example is higher than that of the first and second examples. That is, the third example exhibits a smaller overvoltage than the first and second examples, and an improvement in the energy efficiency of discharge was achieved.

[0079] These improvements in characteristics are believed to be due to the use of positive electrode 101 formed by bonding the positive electrode active material to a co-continuous body, which increases the amount of the positive electrode active material carried.

[0080] <Fourth Example> In the fourth example, a coin-type secondary battery 100a shown in FIG. 2 was fabricated by the following procedure. A polymerized cystine compound was used as the positive electrode active material and supported on a co-continuum. Magnesium (Mg) foil, sodium (Na) foil, and calcium (Ca) foil were used as the negative electrode active materials. A propylene carbonate solution containing 0.5 mol / L of Mg(ClO4)2, NaClO4, and Ca(ClO4)2 was used as the electrolyte 102 for the coin-type secondary battery 100a using magnesium (Mg) foil, sodium (Na) foil, and calcium (Ca) foil.

[0081] The battery was evaluated in the same manner as in Examples 1, 2, and 3. However, the charge / discharge test was continued until the discharge voltage dropped to 0.10V.

[0082] (Preparation of Positive Electrode 101) The co-continuum was immersed in a solution of a polymerized cystine compound dissolved in tetrahydrofuran (THF) (Tokyo Chemical Industry Co., Ltd.). This co-continuum was dried in a vacuum dryer at 80°C for 30 minutes, causing the polymerized cystine compound to precipitate in the co-continuum. This co-continuum containing the polymerized cystine compound was then cut into a circle with a diameter of 16 mm to obtain the positive electrode 101.

[0083] The polymerized cystine compound was produced by first adding ethyl acetate (Tokyo Chemical Industry Co., Ltd.), (1S)-(-)-α-pinene (Tokyo Chemical Industry Co., Ltd.), and bis(trichloromethyl) carbonate (Tokyo Chemical Industry Co., Ltd.) to cystine powder (Tokyo Chemical Industry Co., Ltd.) under an Ar atmosphere, stirring at 90°C for 3 hours, and then filtering off any insoluble matter. Hexane was added to the solution, stirring for 30 minutes, and the precipitated solid was collected by suction filtration. Ethyl acetate and hexane were then added to the resulting residue, stirring for 50 minutes, and the precipitated solid was collected by suction filtration and dried under reduced pressure for 12 hours to obtain N-carboxyanhydride of cystine (NCA). Next, dichloromethane (Tokyo Chemical Industry Co., Ltd.), butylamine (Tokyo Chemical Industry Co., Ltd.), and dichloromethane (Tokyo Chemical Industry Co., Ltd.) were added to the N-carboxyanhydride of cystine under an Ar atmosphere, and the mixture was stirred at 30°C for 12 hours. Thereafter, diethyl ether (Tokyo Chemical Industry Co., Ltd.) was added, and the precipitated solid was collected by suction filtration and dried under reduced pressure for 12 hours to produce a compound in which cystine was polymerized.

[0084] To produce the co-continuum, first, bacterial cellulose gel produced by the acetic acid bacterium Acetobacter xylinum was placed in a test tube and immersed in liquid nitrogen for 30 minutes to completely freeze the bacterial cellulose gel. Next, the frozen bacterial cellulose gel was placed in an eggplant flask and dried in a freeze dryer (Tokyo Rikakikai Co., Ltd.) under a vacuum of less than 10 Pa. The gel was then carbonized by firing at 1200°C for 2 hours in a nitrogen atmosphere to produce a co-continuum.

[0085] (Preparation of Negative Electrode 103) Magnesium (Mg) foil (thickness 150 μm, Nilaco Corporation), sodium (Na) foil (thickness 150 μm, Sigma-Aldrich Co. LLC), and calcium (Ca) foil (thickness 150 μm, Nilaco Corporation) were each cut into a circle with a diameter of 16 mm, and each of these was bonded to copper foil (Nilaco Corporation) using an ultrasonic welding machine to obtain negative electrode 103.

[0086] (Preparation of secondary battery 100) A coin-type secondary battery 100a shown in FIG. 2 was fabricated using a coin battery case (Hosensha).

[0087] A cellulose-based separator (Nippon Kodoshi Kogyo Co., Ltd.) cut to a diameter of 18 mm was placed on the positive electrode case 201 containing the positive electrode 101 prepared by the above method, and a propylene carbonate solution (Kishida Chemical Co., Ltd.) containing Mg(ClO4)2, NaClO4, and Ca(ClO4)2 was poured into the placed separator as the electrolyte 102. The negative electrode 103 was placed on the electrolyte 102, and the negative electrode case 202 was placed over the positive electrode case 201. The peripheral portions of the positive electrode case 201 and the negative electrode case 202 were crimped using a coin cell crimping machine, thereby obtaining a coin-type secondary battery 100a including a propylene gasket 203.

[0088] (Battery performance) The discharge capacity and discharge voltage of the secondary battery of the fourth example are shown in Table 1. As shown in Table 1, the discharge capacity of the battery of the fourth example using magnesium (Mg) in the negative electrode was 212 mAh / g, which was a value greater than those of the first, second, and third examples. The discharge capacities of the batteries using sodium (Na) and calcium (Ca) in the negative electrodes were also greater than those of the first, second, and third examples.

[0089] Furthermore, as shown in Table 1, the discharge voltage of the fourth example is higher than the discharge voltages of the first, second, and third examples. That is, the fourth example exhibits a smaller overvoltage than the first, second, and third examples, and an improvement in the energy efficiency of discharge was achieved.

[0090] Furthermore, as shown in Table 2, the discharge capacity of the fourth example after 20 cycles was 162 mAh / g, which was a larger value than those of the first example, second example, and third example.

[0091] [Table 2]

[0092] These improvements in characteristics are thought to be due to the use of a positive electrode 101 formed by joining polymerized positive electrode active material to the aforementioned co-continuum, which increases the amount of positive electrode active material carried and further makes it more difficult for the positive electrode active material to dissolve in the electrolyte 102 during the electrochemical reaction.

[0093] Furthermore, the secondary battery 100 of this embodiment is a sealed battery that does not require an air intake port, unlike an air battery. Therefore, the secondary battery 100 of this embodiment can be stored for a long period of time without the electrolyte volatilizing through the air intake port.

[0094] Therefore, the secondary battery 100 of this embodiment can be effectively used as a new driving source for various electronic devices such as small devices, sensors, and mobile devices.

[0095] The present invention is not limited to the above-described embodiment, and various modifications are possible within the scope of the present invention. [Explanation of symbols]

[0096] 100: Secondary battery 101: Positive electrode 102: Electrolyte 103: Negative electrode 201: Positive electrode case 202: Negative electrode case 203: Propylene gasket

Claims

1. a positive electrode containing cystine; a negative electrode containing magnesium, sodium, or calcium; an electrolyte disposed between the positive electrode and the negative electrode. Secondary battery.

2. The positive electrode contains a polymer containing a repeating unit represented by formula (1) The secondary battery according to claim 1 . 【Chemical 1】

3. the positive electrode is formed on a porous current collector containing at least one selected from the group consisting of aluminum, copper, and iron, or a nonwoven current collector containing carbon, Contains no binder The secondary battery according to claim 1 .

4. The positive electrode is formed into a bicontinuous structure having a three-dimensional network structure due to a plurality of integrated nanostructures having branches, Contains no binder The secondary battery according to claim 1 .

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