Secondary batteries

Abstract

The present invention provides a secondary battery 100 which comprises: a positive electrode 101 that contains 2,5-dimethoxy-1,4-benzoquinone; a negative electrode 103 that contains magnesium or calcium; and an electrolyte 102 that is disposed between the positive electrode and the negative electrode.

Description

[Technical Field]

[0001] The present disclosure relates to secondary batteries. [Background technology]

[0002] Conventionally, alkaline batteries, manganese batteries, lithium primary batteries, etc. have been widely used as disposable primary batteries in small devices, sensors, mobile equipment, etc. In addition, lithium secondary batteries, nickel-cadmium batteries, nickel-metal hydride batteries, lithium-ion batteries, etc. have been widely used as rechargeable secondary batteries.

[0003] In recent years, with the advancement of the Internet of Things (IoT), progress has been made in the development of scattered sensors that can be installed throughout the natural world, such as in soil or forests. These scattered sensors often use primary batteries, such as coin-type alkaline batteries or primary lithium metal batteries.

[0004] However, primary batteries used in electronic devices such as sensors contain materials that have a high environmental impact, including rare metals and toxic elements, such as lead compounds, cadmium compounds, manganese compounds, nickel compounds, and fluorine compounds, and when discarded, they must follow collection methods set by the national and local governments.

[0005] Therefore, with the aim of applying these batteries to electronic devices such as sensors, studies are being conducted on batteries that are low in cost and environmental impact, using environmentally friendly materials that are abundant in resources; in other words, batteries that are made only of low-environmental-impact materials that can be disposed of as general waste or do not require collection (see Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 6711915 Summary of the Invention [Problem to be solved by the invention]

[0007] Patent Document 1 describes a primary battery that focuses on materials with low environmental impact. However, because an air inlet is required to take in oxygen from the air as a positive electrode active material, the electrolyte inside the battery volatilizes through the air inlet, making it unsuitable for long-term storage. In other words, while conventional primary batteries have a low environmental impact, they have the problem of being unable to be stored for long periods of time.

[0008] On the other hand, conventional secondary batteries can extend the operating time of sensors by using methods such as contactless charging, which is effective in improving the convenience of sensors. However, they have the problem of being highly environmentally hazardous because they use materials that have a high environmental impact, such as rare metals.

[0009] The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide a secondary battery that has a low environmental impact and can be stored for a long period of time. [Means for solving the problem]

[0010] A secondary battery according to one embodiment of the present disclosure includes a positive electrode containing 2,5-dimethoxy-1,4-benzoquinone, a negative electrode containing magnesium or calcium, and an electrolyte disposed between the positive electrode and the negative electrode. The negative electrode further contains carbon black and polyacrylonitrile. . [Effects of the Invention]

[0011] According to the present disclosure, a secondary battery that has a low environmental impact and can be stored for a long period of time can be provided. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram showing the configuration of a secondary battery according to this embodiment. [Figure 2] FIG. 2 is a diagram showing a cross-sectional structure of the coin-type secondary battery according to this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments. Numerous modifications and combinations of the present disclosure are possible within the scope of the gist of the present disclosure.

[0014] [Secondary battery configuration] FIG. 1 is a diagram showing the configuration of a secondary battery according to this embodiment.

[0015] The secondary battery 100 according to this embodiment includes a positive electrode 101 containing 2,5-dimethoxy-1,4-benzoquinone (hereinafter referred to as DMBQ), a negative electrode 103 containing magnesium or calcium, and a non-aqueous electrolyte 102 disposed between the positive electrode 101 and the negative electrode 103.

[0016] The positive electrode 101 may include a positive electrode active material and a current collector, and contains DMBQ as the positive electrode active material. The negative electrode 103 may include a negative electrode active material and a current collector, and contains magnesium or calcium as the negative electrode active material.

[0017] In the secondary battery 100 according to this embodiment, DMBQ contained in the positive electrode 101 and metal ions M responsible for charge transfer from the negative electrode 103 via the electrolyte 102 are mixed. n+ (magnesium ions or calcium ions) bond to each other, causing a discharge reaction to proceed between the positive electrode 101 and the negative electrode 103. During charging, the reaction proceeds in the opposite direction.

[0018] According to this embodiment, DMBQ is used as a positive electrode active material for the positive electrode 101, and magnesium or calcium is used as a negative electrode active material for the negative electrode 103, so that materials that have a high environmental impact, including rare metals and harmful elements, are not required, and a secondary battery 100 with a low environmental impact can be provided.

[0019] Furthermore, according to this embodiment, since DMBQ is used for the positive electrode 101, the secondary battery can be configured as a sealed type, an air intake port for taking in oxygen from the air is not required, and the electrolyte inside the battery does not volatilize through the air intake port, so that the secondary battery 100 can be stored for a long period of time.

[0020] Therefore, according to this embodiment, it is possible to provide a secondary battery 100 that has a low environmental impact and can be stored for a long period of time.

[0021] Furthermore, in this embodiment, the positive electrode 101 is formed on a predetermined current collector. The predetermined current collector is a porous current collector containing at least one selected from the group consisting of aluminum, copper, and iron, a nonwoven current collector containing carbon, or a bicontinuous three-dimensional network structure in which multiple nanostructures are integrated by non-covalent bonds.

[0022] According to this further embodiment, the positive electrode 101 is formed on the above-mentioned specified current collector, so that a large number of reaction sites are ensured in the positive electrode 101, thereby increasing the discharge capacity. As a result, a secondary battery 100 can be provided that exhibits the further effect of fully utilizing the electrochemical activity of DMBQ.

[0023] Furthermore, in this embodiment, carbon black and polyacrylonitrile are added to the negative electrode 103 containing magnesium or calcium.

[0024] According to this further embodiment, the charge / discharge reaction can be enhanced by adding carbon black and polyacrylonitrile to the negative electrode 103. As a result, it is possible to provide a secondary battery 100 that has the further effect of improving the battery performance of the secondary battery 100.

[0025] Furthermore, in this embodiment, the DMBQ contained in the positive electrode 101 is polymerized.

[0026] According to this further embodiment, DMBQ is polymerized, which increases the molecular weight of DMBQ (polymerization). This makes it less likely to be dissolved by the electrolyte 102 during the electrochemical reaction, and excellent chemical stability with little deterioration over a long period of time can be expected. By adjusting the reaction conditions of the polymer compound, the degree of polymerization (molecular weight) of DMBQ can be changed, resulting in even better chemical stability. The molecular weight of the polymer is preferably 10,000 or more, and more preferably 100,000 or more. Therefore, a secondary battery 100 with longer storage life can be provided.

[0027] The electrolyte 102 is not limited to a non-aqueous electrolyte solution, but may be an aqueous electrolyte solution.

[0028] Each component of the secondary battery 100 will be described below.

[0029] (1) Positive electrode The positive electrode 101 of this embodiment contains at least DMBQ as a positive electrode active material, and optionally contains a current collector and a conductive additive.

[0030] For example, the positive electrode 101 is formed without a binder on a porous current collector containing at least one selected from the group consisting of aluminum, copper, and iron. The positive electrode 101 is formed without a binder on a nonwoven current collector containing carbon. The positive electrode 101 is formed without a binder as a co-continuum of a three-dimensional network structure in which multiple nanostructures are integrated by non-covalent bonds. The co-continuum is a three-dimensional network structure in which multiple nanostructures integrated by non-covalent bonds have branches.

[0031] In this way, by forming the positive electrode 101 on a porous current collector, a nonwoven current collector, or a bicontinuous body with a three-dimensional network structure without a binder, the electrochemical activity of the positive electrode active material DMBQ can be fully exploited.

[0032] The positive electrode 101 may be formed with a binder, but is preferably formed without a binder. When formed with a binder, binders such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene butadiene rubber, ethylene propylene diene rubber, and natural rubber are used.

[0033] (1-1) Positive electrode active material The positive electrode active material contains at least DMBQ, which does not contain rare metals and is therefore environmentally friendly and inexpensive.

[0034] Furthermore, the positive electrode active material is preferably in a polymeric state. This is because a positive electrode active material with a small molecular weight is easily dissolved in the electrolyte. Therefore, the molecular weight of DMBQ is increased by polymerizing DMBQ. The molecular weight of DMBQ is preferably 10,000 or more, more preferably 100,000 or more. DMBQ may be commercially available or may be synthesized by a known method.

[0035] (1-2) Preparation of positive electrode using conductive additive The positive electrode 101 may contain a conductive additive, such as carbon. Examples of the conductive additive include carbon blacks such as ketjen black and acetylene black, activated carbons, graphites, and carbon fibers.

[0036] To ensure a sufficient conductive path within the positive electrode 101, the carbon preferably has small particles. Specifically, the particle diameter is preferably 1 μm or less. The carbon may be commercially available or may be synthesized by a known method.

[0037] (1-3) Preparation of positive electrode using current collector The positive electrode 101 may include a current collector. The current collector is a porous current collector containing at least one selected from the group consisting of aluminum, copper, and iron, or a nonwoven fabric current collector containing carbon. The positive electrode 101 is formed on such a current collector.

[0038] The positive electrode 101 is preferably formed on such a current collector without a binder. Specifically, the positive electrode active material DMBQ is directly supported on such a current collector. Direct support means that the positive electrode active material is bonded to the current collector in a three-dimensional structure, thereby improving conductivity. Commercially available porous current collectors and nonwoven fabric current collectors can be used.

[0039] Additionally, the current collector is a co-continuum with a three-dimensional network structure in which multiple nanostructures are integrated by non-covalent bonds. The positive electrode 101 is preferably formed on this co-continuum without a binder. Specifically, the positive electrode active material DMBQ is directly supported on this co-continuum. The co-continuum has a flexible, integrated structure in which the bonding portions between the nanostructures are deformable. The co-continuum preferably has an average pore size of 0.1 μm to 50 μm, for example.

[0040] The nanostructures are, for example, nanosheets or nanofibers, and are electrically conductive. An example of a nanosheet is graphene. Graphene nanofibers are fibrous materials with a diameter of 1 nm to 1 μm and a length 100 times or more the diameter. Examples of nanofibers are iron oxide, manganese oxide, silicon, and carbonized cellulose. Carbonized cellulose can be produced by producing a gel in which cellulose nanofibers are dispersed, and then heating this gel in an inert gas atmosphere to carbonize it.

[0041] The 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.

[0042] The dispersion medium for the sol may be, for example, an aqueous medium such as water (HO), or an organic medium such as carboxylic acid, methanol (CHOH), ethanol (CHOH), propanol (CHOH), n-butanol, isobutanol, n-butylamine, dodecane, unsaturated fatty acid, ethylene glycol, heptane, hexadecane, isoamyl alcohol, octanol, isopropanol, acetone, or glycerin, or two or more of these may be mixed.

[0043] The dispersion medium for the gel is, for example, an aqueous medium such as water, or an organic medium 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, and two or more of these may be mixed.

[0044] The degree of vacuum in the drying process varies depending on the type of dispersion medium used, but it is sufficient as long as the dispersion medium sublimes. For example, if water is used as the dispersion medium, the pressure must be 0.06 MPa or less, 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 Pa~1.0×10 ―2 Preferably, the drying temperature is 100 Pa. Furthermore, heat may be applied using a heater or the like during drying.

[0045] The three-dimensional network structure of the co-continuum allows for 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 200m 2 / g or more. The co-continuum is also called a copolymer.

[0046] The following methods can be considered for supporting a positive electrode active material on the above-mentioned porous current collector, nonwoven fabric current collector, and co-continuous body of a three-dimensional network structure.

[0047] For example, physical methods such as vapor deposition, sputtering, and planetary ball milling, methods in which the porous current collector, nonwoven fabric current collector, and co-continuous body are immersed in a liquid in which a positive electrode active material is dissolved and then dried, chemical methods such as a sol-gel method, and known methods are available.

[0048] To easily form a high-quality positive electrode 101, a preferred method is to impregnate the above-mentioned porous current collector, nonwoven fabric current collector, or bicontinuous body with a three-dimensional network structure with a liquid containing a dissolved positive electrode active material, and then dry the impregnated material to support the positive electrode active material. In this case, the dried electrode may be subjected to cold pressing or hot pressing. This increases the strength of the electrode, resulting in a more stable positive electrode.

[0049] Generally, electrodes for commercial batteries such as lithium-ion batteries are produced by adjusting the viscosity of a slurry containing an active material, conductive additive, binder, and organic solvent to an appropriate level for application, applying it to a metal foil (such as aluminum or copper foil) as a current collector foil using a coater or similar tool, and then drying it. The thickness and mass of the electrode have a significant effect on the battery's energy density; the thicker the coating, the greater the capacity and the lower the rate characteristics; the thinner the coating, the better the rate characteristics but the lower the capacity.

[0050] On the other hand, in this embodiment, a porous current collector, a carbon-containing nonwoven current collector, and a bicontinuous three-dimensional network structure in which multiple nanostructures are integrated are used, which allows for a thicker film than the above-mentioned coated electrode, contributing to a higher battery capacity. In addition, because the battery can be fabricated without using a current collector foil, it is possible to reduce the cost of the battery.

[0051] The solvent for dissolving the positive electrode active material is, for example, 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, and two or more of these may be mixed.

[0052] In the secondary battery 100 according to this embodiment, the reaction proceeds on the surface of the positive electrode 101, so it is considered preferable to generate a large number of reaction sites inside the positive electrode 101. In this regard, when the specific surface area of ​​the positive electrode 101 formed using the conductive additives and binders described above is increased, the binding strength between the conductive additives decreases, causing structural deterioration, making stable discharge difficult and reducing the discharge capacity. Because the binder is an insulating substance, the inclusion of a large amount of binder reduces the conductivity, leading to a decrease in battery performance such as discharge voltage and discharge capacity. Furthermore, when Ketjenblack powder is used as the conductive additive, it is difficult to increase the specific surface area from the viewpoint of binding strength.

[0053] In contrast, the positive electrode 101 formed using the porous current collector, nonwoven current collector, or co-continuous body with a three-dimensional network structure described above provides a large number of reaction sites, thereby solving the above-mentioned problems and increasing the discharge capacity. In particular, the co-continuous body has a high bulk density and can support a larger amount of positive electrode active material, thereby improving the efficiency of the battery.

[0054] As described above, the positive electrode 101 is formed on a porous current collector, a nonwoven current collector, or a bicontinuous body with a three-dimensional network structure, so that the electrochemical activity of the positive electrode active material, DMBQ, can be fully exploited.

[0055] (2) Negative electrode The negative electrode 103 of this embodiment contains at least magnesium (Mg) or calcium (Ca) as a negative electrode active material. The negative electrode active material may contain magnesium or calcium as a main component, and may also contain an alloy containing at least one component selected from the group consisting of lithium (Li), sodium (Na), zinc (Zn), aluminum (Al), manganese (Mn), iron (Fe), tin (Sn), and carbon (C).

[0056] Furthermore, the activity of magnesium or calcium in the charge-discharge reaction is improved, and battery performance is improved, by adding carbon black or polyacrylonitrile (PAN) to the negative electrode 103. The most effective addition of PAN is achieved when the amount of PAN added is 5% to 15% of the total weight of the negative electrode.

[0057] Although the negative electrode metal is usually filled in excess of the positive electrode capacity, the addition of PAN improves the utilization efficiency of the negative electrode metal, which has the advantages of increasing the energy density of the battery and reducing the metal filling amount, thereby reducing costs. Furthermore, because the surface of the negative electrode metal is covered with PAN, short-circuiting between the positive electrode 101 and the negative electrode 103 is prevented even when the battery is subjected to an impact, and this is expected to improve safety.

[0058] (3) Electrolyte The electrolyte 102 of this embodiment is a non-aqueous electrolyte solution. The non-aqueous electrolyte solution contains magnesium ions (Mg 2+ ), or calcium ions (Ca 2+ ) is a solution containing an electrolyte that allows the movement of

[0059] 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 may be, for example, an electrolyte solution obtained by dissolving a magnesium salt or a calcium salt in at least one organic solvent 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).

[0060] The magnesium salt and calcium salt are represented by Mg-X2 and Ca-X2, respectively. X can be, 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), R 1 FBF3 (However, R 1 F=nC m F 2m+1 , m = natural number from 1 to 4), R 2 BF3 (However, R 2 =nC p H 2p+1 , p=a natural number of 1 to 5). Furthermore, metal salts in which two or more of these are mixed can be used.

[0061] 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.

[0062] (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 may be conventionally known materials, but from the perspective of environmental impact and waste disposal, they preferably do not contain hazardous substances, rare metals, etc. Furthermore, it is more preferable that these other elements are biologically derived and biodegradable materials.

[0063] (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 a non-aqueous electrolyte 102, and 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.

[0064] The secondary battery 100 having such a configuration can be prepared in the same manner as a conventional secondary battery. For example, the secondary battery may be prepared by assembling a positive electrode 101 containing DMBQ, a negative electrode 103 containing magnesium or calcium, and a non-aqueous electrolyte 102 disposed so as to be in contact with the positive electrode 101 and the negative electrode 103 according to a conventional technique.

[0065] As an embodiment of the method for manufacturing a secondary battery, for example, a coin-type secondary battery can be manufactured.

[0066] 2 is a diagram showing the cross-sectional structure of a coin-type secondary battery. First, a positive electrode 101 is placed in a positive electrode case 201, a separator (not shown) is placed on top of it, and an electrolyte 102 is poured onto the separator. Next, a negative electrode 103 is placed on the electrolyte 102, and the negative electrode case 202 is placed over the positive electrode case 201. Finally, the peripheral portions of the positive electrode case 201 and the negative electrode case 202 are crimped using a coin cell crimping machine. A propylene gasket 203 is inserted into the peripheral portions, and the interior is sealed by the propylene gasket 203.

[0067] [Example] Examples of the secondary battery 100 according to this embodiment will be described below. In each of the following examples, three types of secondary batteries 100 were fabricated using magnesium or calcium for the negative electrode 103 and a propylene carbonate solution containing Mg[N(SOCF)] or Ca[N(SOCF)] for the non-aqueous electrolyte 102.

[0068] Example 1 In Example 1, a coin-type secondary battery was fabricated using the following procedure. The positive electrode 101 was prepared by pressing DMBQ as the positive electrode active material onto a copper-containing porous current collector (copper mesh, CU-118016, Nilaco Corporation). The negative electrode 103 was prepared by using magnesium powder and calcium lump as the negative electrode active materials. The nonaqueous electrolyte 102 was a propylene carbonate solution containing 0.5 mol / L of Mg[N(SO2CF3)2]2 and Ca[N(SO2CF3)2]2.

[0069] (Preparation of positive electrode) The DMBQ powder (Sigma-Aldrich Co. LLC), Ketjenblack powder (EC600JD, Lion Specialty Chemicals Co., Ltd.), and polytetrafluoroethylene (PTFE) powder were thoroughly crushed and mixed in a weight ratio of 80:10:10 using a grinder, and then roll-formed into a sheet electrode (thickness: 0.5 mm). The sheet electrode and a copper mesh current collector were each cut into a circle with a diameter of 16 mm, and the circular sheet electrode was pressed onto a circular copper mesh to obtain a positive electrode.

[0070] (Preparation of negative electrode) Magnesium powder (Nilaco Corporation), carbon black, and polyacrylonitrile (PAN) powder (Sigma-Aldrich Co. LLC) were mixed in a weight ratio of 80:10:10 and dissolved in dimethylformaldehyde (DMF) to prepare a mixture. After stirring the mixture for 5 hours with a magnetic stirrer, it was applied to a copper foil current collector (Nilaco Corporation), annealed at 300°C in an inert atmosphere, and cut into a 16 mm diameter circle to obtain a negative electrode.

[0071] A negative electrode using calcium lump (Kanto Chemical Co., Ltd.) was also prepared using the same preparation method as that using magnesium powder.

[0072] (Preparation of secondary battery) A coin-type secondary battery was fabricated using a coin battery case (Hosen Co., Ltd.).

[0073] The prepared positive electrode 101 was placed in a positive electrode case 201, and a cellulose-based separator (Nippon Kodoshi Kogyo Co., Ltd.) cut to a diameter of 18 mm was placed on the positive electrode 101. A propylene carbonate solution (Kishida Chemical Co., Ltd.) containing Mg[N(SOCF)] and Ca[N(SOCF)] was poured onto the separator as a non-aqueous electrolyte 102. The prepared 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 whose interior was sealed with a propylene gasket 203.

[0074] (Battery performance evaluation) The battery performance of the secondary battery prepared by the above procedure was measured. The battery cycle test was performed using a charge / discharge measurement system (VMP-3, manufactured by BioLogic) at a current density of 0.1 mA / cm per effective area of ​​the positive electrode 101. 2The discharge voltage was measured until the battery voltage decreased from the open circuit voltage to 0.10 V (discharge end voltage). The charge was performed at a current density of 0.1 mA / cm per effective area of ​​the positive electrode 101. 2 The charge cut-off voltage was set to 3.0 V. The charge / discharge test of the battery was carried out under normal living conditions. The charge / discharge capacity was expressed as the value (mAh / g) per unit weight of the positive electrode active material (DMBQ).

[0075] The discharge capacity and discharge voltage of the secondary battery 100 of Example 1 are shown in Table 1.

[0076] [Table 1] As shown in Table 1, the discharge voltages of the negative electrodes 103 using magnesium and calcium were 1.82 V and 2.05 V, respectively, and the discharge capacities were 96 mAh / g and 114 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 100 of Example 1 had excellent battery performance.

[0077] <Example 2> In Example 2, a coin-type secondary battery was fabricated by the following procedure. The positive electrode 101 was prepared by using DMBQ powder as the positive electrode active material and supporting the DMBQ powder on a carbon-containing nonwoven current collector (carbon felt). The negative electrode 103 and nonaqueous electrolyte 102 were the same as those in Example 1.

[0078] (Preparation of positive electrode) Carbon felt (Toyobo Co., Ltd.) was immersed in a solution prepared by dissolving DMBQ powder (Sigma-Aldrich Co. LLC) obtained by the same procedure as in Example 1 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 DMBQ on the carbon felt, and then washed with pure water. The DMBQ-containing carbon felt was then cut into a circle with a diameter of 16 mm to obtain a positive electrode.

[0079] (Preparation of negative electrode) The negative electrode 103 was prepared by the same preparation method as in Example 1.

[0080] (Preparation of secondary battery) The secondary battery 100 was fabricated using the same adjustment method as in Example 1.

[0081] (Battery performance evaluation) The battery performance was evaluated using the same evaluation method as in Example 1. The discharge capacity and discharge voltage of the secondary battery 100 of Example 2 are included in Table 1 above. As shown in Table 1, the discharge capacity of Example 2, in which magnesium was used for the negative electrode 103, was 131 mAh / g, which was a larger value than that of Example 1. Even when calcium was used for the negative electrode, the discharge capacity was larger than that of Example 1.

[0082] Furthermore, as shown in Table 1, the discharge voltage of Example 2 is higher than that of Example 1. That is, Example 2 exhibits a smaller overvoltage than Example 1, and an improvement in discharge energy efficiency was achieved.

[0083] These improvements in characteristics are believed to be due to the use of positive electrode 101 formed by supporting DMBQ, a positive electrode active material, on carbon felt, which reduced the internal resistance of the battery and allowed the battery reaction to proceed efficiently.

[0084] Example 3 In Example 3, a coin-type secondary battery was fabricated by the following procedure. The positive electrode 101 was prepared by using DMBQ powder as the positive electrode active material and supporting the DMBQ powder in a bicontinuous three-dimensional network structure in which multiple nanostructures were integrated. The negative electrode 103 and nonaqueous electrolyte 102 were the same as those in Example 1.

[0085] (Preparation of positive electrode) The resulting DMBQ powder (Sigma-Aldrich Co. LLC) was dissolved in 1.0 M hydrochloric acid (Tokyo Chemical Industry Co., Ltd.) to form a three-dimensional network structure. The resulting co-continuum was then immersed in the solution. The co-continuum was dried in a vacuum oven at 80°C for 30 minutes to precipitate DMBQ, followed by rinsing with pure water. The DMBQ-containing co-continuum was then cut into a 16 mm diameter circle to obtain a positive electrode.

[0086] To produce the co-continuum, bacterial cellulose gel produced by the acetic acid bacterium Acetobacter xylinum was placed in a test tube and completely frozen by immersing the test tube in liquid nitrogen for 30 minutes. The frozen bacterial cellulose gel was then transferred to an eggplant flask and dried in a freeze dryer (Tokyo Rikakikai Co., Ltd.) under a vacuum of 10 Pa or less. The gel was then carbonized by baking at 1200°C for 2 hours in a nitrogen atmosphere to produce the co-continuum.

[0087] (Preparation of negative electrode) The negative electrode 103 was prepared by the same preparation method as in Example 1.

[0088] (Preparation of secondary battery) The secondary battery 100 was fabricated using the same adjustment method as in Example 1.

[0089] (Battery performance evaluation) The battery performance was evaluated using the same evaluation method as in Example 1. The discharge capacity and discharge voltage of the secondary battery 100 of Example 3 are included in Table 1 above. As shown in Table 1, the discharge capacity of Example 3, in which magnesium was used for the negative electrode 103, was 178 mAh / g, which was a larger value than those of Examples 1 and 2. Even when calcium was used for the negative electrode 103, the discharge capacity was larger than those of Examples 1 and 2.

[0090] Furthermore, as shown in Table 1, the discharge voltage of Example 3 is higher than the discharge voltages of Examples 1 and 2. That is, Example 3 exhibits a smaller overvoltage than Examples 1 and 2, and an improvement in discharge output characteristics was achieved.

[0091] These improvements in characteristics are believed to be due to the improved dispersibility of the positive electrode active material, which is achieved by using positive electrode 101 formed by supporting the positive electrode active material, DMBQ, on the co-continuum.

[0092] Table 2 shows the discharge capacity after 20 cycles.

[0093] [Table 2] The discharge capacity after 20 cycles of Example 3, in which magnesium was used for the negative electrode 103, was 161 mAh / g, which was a value greater than those of Examples 1 and 2. Even when calcium was used for the negative electrode 103, the value was greater than those of Examples 1 and 2.

[0094] These improvements in characteristics are thought to be due to the use of positive electrode 101 formed by supporting the positive electrode active material DMBQ on the above-mentioned co-continuum, which improved the dispersibility of the positive electrode active material and, further, improved the dissolution of the positive electrode active material into the electrolyte solution during the electrochemical reaction.

[0095] <Comparative Example 1> In Comparative Example 1, a coin-type secondary battery that did not use magnesium powder or calcium lumps in the negative electrode was fabricated in the same manner as in Example 1. The secondary battery was evaluated in the same manner as in Example 1.

[0096] For the positive electrode, DMBQ powder (Sigma-Aldrich Co. LLC), Ketjenblack powder (EC600JD, Lion Specialty Chemicals Co., Ltd.), and polytetrafluoroethylene (PTFE) powder were thoroughly crushed and mixed in a weight ratio of 80:10:10 using a grinder, and then roll-formed into a sheet electrode (thickness: 0.5 mm). The sheet electrode was cut into a circle with a diameter of 16 mm and pressed onto a copper mesh to obtain a positive electrode.

[0097] For the negative electrode, magnesium powder or calcium blocks were not used. Instead, magnesium foil (150 μm thick, Nilaco Corporation) and calcium foil (150 μm thick) were cut into 16 mm diameter circles, and each was bonded to copper foil (Nilaco Corporation) using an ultrasonic welder. The calcium foil was made by rolling commercially available calcium powder.

[0098] The rest is the same as in the first embodiment.

[0099] The discharge capacities and discharge voltages of the secondary batteries of Comparative Example 1 are included in Table 1. As shown in Table 1, the discharge voltages of Comparative Example 1, in which magnesium foil and calcium foil were used as the negative electrodes, were 1.13 V and 1.29 V, and the discharge capacities were 62 mAh / g and 119 mAh / g. Furthermore, as shown in Table 2, the discharge capacities after 20 cycles were 19 mAh / g and 30 mAh / g.

[0100] Comparative Example 1 had lower discharge voltage, discharge capacity, and discharge capacity after 20 cycles than Examples 1 to 3. On the other hand, in Examples 1 to 3, the use of metal powder, carbon black, and polyacrylonitrile (PAN) in the negative electrode reduced the contact area between the metal and the electrolyte, thereby suppressing metal corrosion, which reduced charge / discharge overvoltage and improved charge / discharge energy efficiency, which is thought to have resulted in improved discharge voltage, discharge capacity, and discharge capacity after 20 cycles.

[0101] [Effects of the embodiment] According to this embodiment, DMBQ is used as a positive electrode active material for the positive electrode 101, and magnesium or calcium is used as a negative electrode active material for the negative electrode 103, so that materials that have a high environmental impact, including rare metals and harmful elements, are not required, and a secondary battery 100 with a low environmental impact can be provided.

[0102] According to this embodiment, since DMBQ is used as the positive electrode active material for the positive electrode 101, the secondary battery can be configured as a sealed type, an air intake port for taking in oxygen from the air is not required, and the electrolyte solution inside the battery (when the electrolyte 102 is aqueous) does not volatilize from the air intake port, so a secondary battery 100 that can be stored for a long period of time can be provided.

[0103] According to this embodiment, the positive electrode 101 is formed on a porous current collector containing at least one selected from the group consisting of aluminum, copper, and iron, a nonwoven current collector containing carbon, or a bicontinuous three-dimensional network structure in which multiple nanostructures are integrated by noncovalent bonds, thereby ensuring a large number of reaction sites in the positive electrode 101 and increasing the discharge capacity. As a result, a secondary battery 100 can be provided that has the additional effect of fully utilizing the electrochemical activity of DMBQ.

[0104] According to this embodiment, carbon black and polyacrylonitrile are added to the negative electrode 103 containing magnesium or calcium, thereby enhancing the charge-discharge reaction. As a result, it is possible to provide a secondary battery 100 that has the further effect of improving the battery performance of the secondary battery 100.

[0105] According to this embodiment, the DMBQ contained in the positive electrode 101 is polymerized, so that the molecular weight of the DMBQ increases (polymerization), making it less likely to be dissolved by the electrolyte 102 in an electrochemical reaction, and excellent chemical stability with little deterioration over a long period of time can be expected.

[0106] [Application areas] The secondary battery 100 according to this embodiment can be effectively used as a new driving source for various electronic devices such as small devices, sensors, and mobile devices. [Explanation of symbols]

[0107] 100 Secondary battery 101 Positive electrode 102 Electrolytes 103 Negative electrode 201 Positive electrode case 202 Negative electrode case 203 Propylene Gasket

Claims

1. a positive electrode containing 2,5-dimethoxy-1,4-benzoquinone; a negative electrode containing magnesium or calcium; an electrolyte disposed between the positive electrode and the negative electrode; The negative electrode is The secondary battery further comprises carbon black and polyacrylonitrile.

2. The positive electrode is 2. The secondary battery according to claim 1, wherein the electrode is formed on a porous current collector containing at least one material selected from the group consisting of aluminum, copper, and iron.

3. The positive electrode is 2. The secondary battery according to claim 1, wherein the secondary battery is formed on a nonwoven current collector containing carbon.

4. The positive electrode is The secondary battery according to claim 1 , wherein a plurality of nanostructures are formed into a co-continuous three-dimensional network structure.

5. The 2,5-dimethoxy-1,4-benzoquinone is 10. The secondary battery according to claim 1, which is polymerized.

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