Electrochemical device

Abstract

Provided is an electrochemical device including a negative electrode, a positive electrode, and a separator disposed between the negative electrode and the positive electrode. In the electrochemical device of the present invention, the negative electrode is an electrode containing magnesium and is in contact with a fullerene-containing layer containing a fullerene. The electrolyte of the electrochemical device contains a solvent and a magnesium salt contained in the solvent.

Description

Technical Field

[0001] This invention relates to an electrochemical device. Background Technology

[0002] Electrochemical devices include capacitors, air batteries, fuel cells, and secondary batteries, and are used for various applications. An electrochemical device has a positive electrode and a negative electrode, and an electrolyte for transporting ions between the positive and negative electrodes.

[0003] For example, as electrodes in electrochemical devices, such as magnesium batteries, electrodes made of magnesium or containing at least magnesium are used (hereinafter, such electrodes are also referred to as "magnesium-containing electrodes" or simply "magnesium electrodes," and electrochemical devices using magnesium-containing electrodes are also referred to as "magnesium electrode-based electrochemical devices"). Magnesium is more abundant and cheaper than lithium. Furthermore, magnesium generally yields a larger amount of electricity per unit volume through redox reactions, and it is also safer when used in electrochemical devices. Therefore, magnesium batteries are attracting attention as a next-generation secondary battery to replace lithium-ion batteries.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: US Patent Publication US2013 / 252112A1 Summary of the Invention

[0007] The technical problem that the invention aims to solve

[0008] The inventors of this application have noticed that there are still technical problems that need to be overcome in magnesium batteries, and have found that it is necessary to take corresponding countermeasures. Specifically, the inventors of this application have discovered the following technical problems.

[0009] In magnesium batteries using magnesium as the negative electrode, improving cycle performance is one of the important technical challenges. While this can be addressed by changing the types of Mg electrolyte and positive electrode materials, the current focus remains on improving cycle performance.

[0010] While lithium-ion batteries, widely used as rechargeable batteries, can have their cycle characteristics improved by adding additives to the electrolyte, this approach is less effective for magnesium batteries. This is because the Mg coordination structure in magnesium battery electrolytes is very fragile, tending to impair the activity of Mg precipitation and dissolution by additives used in lithium-ion batteries. In other words, it is generally difficult to improve the cycle characteristics of magnesium battery electrolytes.

[0011] Furthermore, improving energy density is also a significant technical challenge in magnesium batteries. In particular, the initial discharge voltage can sometimes be reduced due to negative electrode overvoltage, and such voltage drop cannot be adequately suppressed.

[0012] The present invention was made in view of the above-mentioned technical problems. That is, the main objective of the present invention is to provide an electrochemical device having a magnesium-containing electrode and exhibiting excellent cycle characteristics and higher energy density.

[0013] Technical solutions for solving technical problems

[0014] The inventors of this application sought to solve the aforementioned technical problems by taking steps in a new direction, rather than extending from the prior art. As a result, an invention of an electrolyte that achieves the aforementioned main objectives was completed.

[0015] In this invention,

[0016] An electrochemical device is provided, comprising a negative electrode, a positive electrode, and a membrane disposed between the negative electrode and the positive electrode.

[0017] The negative electrode is a magnesium-containing electrode.

[0018] The electrolyte of the electrochemical device comprises a solvent and a magnesium salt contained in the solvent.

[0019] The negative electrode is in contact with a fullerene-containing layer.

[0020] The effects of the invention

[0021] The electrochemical device of the present invention provides an electrochemical device with improved cycle characteristics and energy density. That is, although the electrochemical device of the present invention is a so-called "magnesium electrode system", it further improves the cycle characteristics and energy density. This improved cycle characteristics and energy density make the magnesium electrode system electrochemical device more suitable for use in practical environments.

[0022] It should be noted that the effects described in this manual are only examples and are not limited to them. In addition, there may be additional effects. Attached Figure Description

[0023] Figure 1 This is a conceptual diagram of an electrochemical device (particularly a battery) with a magnesium electrode system according to one embodiment of the present invention.

[0024] Figure 2 This is a schematic cross-sectional view of a magnesium secondary battery (cylindrical magnesium secondary battery) provided as an embodiment of the present invention.

[0025] Figure 3This is a schematic perspective view of a magnesium secondary battery (flat-plate laminated film magnesium secondary battery) provided as an embodiment of the present invention.

[0026] Figure 4 This is a schematic cross-sectional view of an electrochemical device provided as a capacitor in one embodiment of the present invention.

[0027] Figure 5 This is a schematic cross-sectional view of an electrochemical device provided as an air battery in one embodiment of the present invention.

[0028] Figure 6 This is a schematic cross-sectional view of an electrochemical device provided as a fuel cell in one embodiment of the present invention.

[0029] Figure 7 This is a block diagram illustrating an example of a circuit structure when the magnesium secondary battery provided as an embodiment of the present invention is applied to a battery pack.

[0030] Figure 8 A, Figure 8 B and Figure 8 C is a block diagram showing the structure of an electric vehicle, an energy storage system, and a power tool that utilize magnesium secondary batteries as one embodiment of the present invention.

[0031] Figure 9 This is a schematic diagram showing the unfolded battery manufactured in the "Examples" of this specification.

[0032] Figure 10 This indicates the results of the charge-discharge curves obtained in the "Examples" of this specification (Example 1).

[0033] Figure 11 This indicates the results of the charge-discharge curves obtained in the "Examples" of this specification (Example 2).

[0034] Figure 12 The results of the charge-discharge curves obtained in the "Examples" of this specification (Comparative Example 1) are shown.

[0035] Figure 13 This indicates the relationship between specific capacity and discharge voltage obtained in the "Examples" of this specification (Example 3 and Comparative Example 2).

[0036] Figure 14 This is a schematic cross-sectional view showing how a fullerene-containing layer partially covers the negative electrode. Detailed Implementation

[0037] The following describes in detail the "electrochemical device" according to embodiments of the present invention. Although the description is based on the accompanying drawings as needed, the illustrations are merely schematic and illustrative for the purpose of understanding the present invention, and the appearance and size ratios may differ from the actual object.

[0038] In this specification, all numerical ranges mentioned, unless accompanied by special terms such as "less than", "greater than", or "greater than", refer to the values ​​themselves, including both the lower and upper limits (i.e., the upper and lower limits). For example, a numerical range of 1 to 10 is interpreted as including the lower limit "1" and the upper limit "10".

[0039] In this invention, "electrochemical device" broadly refers to a device capable of extracting energy through electrochemical reactions. In a narrower sense, "electrochemical device" in this invention refers to a device having a pair of electrodes and an electrolyte, particularly one that charges and discharges via the movement of ions. While merely an example, examples of electrochemical devices include, in addition to secondary batteries, capacitors, air batteries, and fuel cells.

[0040] [Electrochemical device]

[0041] The electrochemical device involved in the embodiments of the present invention (hereinafter also referred to as "this embodiment") is a device capable of extracting energy using an electrochemical reaction.

[0042] The electrochemical device involved in this embodiment is an electrochemical device having a negative electrode, a positive electrode, and a membrane disposed between the negative electrode and the positive electrode. As will be described later, in the electrochemical device involved in this embodiment, the negative electrode is preferably a magnesium-containing electrode, and the positive electrode is a sulfur-containing electrode, i.e., a sulfur electrode. That is, in a preferred embodiment, the electrochemical device involved in this embodiment is an electrochemical device with a magnesium (Mg)-sulfur (S) electrode.

[0043] In this specification, the term "sulfur electrode" broadly refers to an electrode having sulfur (S) as an active component (i.e., an active substance). In a narrower sense, "sulfur electrode" refers to an electrode containing at least sulfur, such as an electrode containing S8 and / or polymeric sulfur, and particularly a positive electrode.

[0044] The sulfur electrode may contain components other than sulfur, such as conductive additives and / or binders. Although this is just an example, the sulfur content in the sulfur electrode, based on the entire electrode, is preferably 5% by mass or more and 95% by mass or less, for example, about 70% by mass or more and 90% by mass or less.

[0045] As conductive additives, examples of carbon materials include graphite, carbon fiber, carbon black, and carbon nanotubes; one or more of these materials can be used. For example, vapor-grown carbon fiber (VGCF (registered trademark)) can be used. For example, acetylene black and / or Ketjen black can be used. For example, multi-walled carbon nanotubes (MWCNTs), such as single-walled carbon nanotubes (SWCNTs) and / or double-walled carbon nanotubes (DWCNTs), can be used. Materials other than carbon materials can also be used, as long as they have good conductivity; for example, metallic materials such as Ni powder and / or conductive polymers can be used.

[0046] Examples of adhesives include fluorinated resins such as polyvinylidene fluoride (PVdF) and / or polytetrafluoroethylene (PTFE), polyvinyl alcohol (PVA) resins, and / or styrene-butadiene copolymer (SBR) resins. Additionally, conductive polymers can also be used as adhesives. Examples of conductive polymers include substituted or unsubstituted polyaniline, polypyrrole, polythiophene, and (co)polymers composed of one or two of these.

[0047] Furthermore, the term "magnesium-containing electrode" as used in this specification broadly refers to an electrode having magnesium (Mg) as an active ingredient (i.e., an active substance). In a narrower sense, "magnesium-containing electrode" refers to an electrode made of magnesium, such as an electrode containing magnesium metal or a magnesium alloy, particularly a negative electrode. It should be noted that while such magnesium-containing electrodes may also contain components other than magnesium metal or magnesium alloys, in a preferred embodiment they are electrodes made of a magnesium metallic body (e.g., an electrode made of a monomer of magnesium metal with a purity of 90% or more, preferably 95% or more, and more preferably 98% or more).

[0048] The material constituting the negative electrode (specifically, the negative electrode active material) is a "magnesium-containing electrode," and is therefore preferably composed of magnesium metal monomers, magnesium alloys, or magnesium compounds. When the negative electrode is composed of magnesium metal monomers (e.g., magnesium plates), the Mg purity of these monomers is, for example, 90% or more, preferably 95% or more, and more preferably 98% or more. The negative electrode can be made from, for example, plate-shaped or foil-shaped materials, but is not limited to these; it can also be formed (formed) using powder.

[0049] The negative electrode can also employ a structure in which a negative electrode active material layer is formed near its surface. For example, the negative electrode includes a layer with magnesium ion conductivity as the negative electrode active material layer, which contains magnesium (Mg) and also contains at least one of carbon (C), oxygen (O), sulfur (S), and halogens. Such a negative electrode active material layer is merely an example and can have a single peak originating from magnesium in the range of 40 eV to 60 eV. As a halogen, at least one selected from the group consisting of fluorine (F), chlorine (Cl), bromine (Br), and iodine (I) can be listed. In this case, the negative electrode active material layer can be extended 2 × 10⁻⁶ meters from its surface to a direction perpendicular to the surface (depth direction). -7 Within a depth range of m, a single peak originating from magnesium is observed in the range above 40 eV and below 60 eV. This is because the negative electrode active material layer exhibits good electrochemical activity from its surface to its interior. Furthermore, for the same reason, the oxidation state of magnesium can also be observed in a range of 2 × 10⁻⁶ eV from the surface of the negative electrode active material layer towards its depth. -7 The value of m remains approximately constant within a certain range. Here, the surface of the negative electrode active material layer refers to the side of the negative electrode active material layer that forms the electrode surface, and the back side refers to the side opposite to that surface, i.e., the side that forms the interface between the current collector and the negative electrode active material layer. Whether the negative electrode active material layer contains the aforementioned elements can be confirmed using XPS (X-ray Photoelectron Spectroscopy). Furthermore, XPS can also confirm that the negative electrode active material layer has the aforementioned peaks and exhibits a magnesium oxidation state.

[0050] In the electrochemical device according to this embodiment, the positive and negative electrodes are separated by a membrane that prevents short circuits caused by contact between the two electrodes while allowing magnesium ions to pass through. Such a membrane can be an inorganic membrane and / or an organic membrane. Examples of inorganic membranes include glass filters and glass fibers. Examples of organic membranes include porous membranes made of synthetic resins such as polytetrafluoroethylene, polypropylene, and / or polyethylene, or structures formed by stacking two or more of these porous membranes. Among these, porous membranes made of polyolefins are preferred because they offer excellent short-circuit prevention and improve battery safety through a circuit-breaking effect.

[0051] In the electrochemical device according to this embodiment, the negative electrode is in contact with a fullerene-containing layer. In this embodiment, because the negative electrode of the electrochemical device is in contact with a fullerene, the cycle characteristics and energy density can be improved.

[0052] The fullerene-containing layer can be a continuous or partial layer covering the target electrode. The fullerene-containing layer can contact the negative electrode in two ways: first, as a capping layer covering the negative electrode; and second, as a separator. It should be noted that the first and second methods can also be combined. When the fullerene-containing layer is a separator and / or a capping layer covering the negative electrode, the electrochemical device of the magnesium electrode system according to this embodiment is more likely to exhibit higher cycle characteristics and energy density.

[0053] In the first approach, the fullerene-containing layer is a capping layer covering the negative electrode. The fullerene-containing layer contains fullerenes, or may be composed of fullerenes. The fullerene-containing layer may, for example, continuously cover the negative electrode surface, or it may partially cover the negative electrode surface, leaving a portion of the negative electrode surface exposed. The manner in which the negative electrode surface is continuously or partially covered can be confirmed, for example, by electron microscopy. It should be noted that "fullerenes" can be identified by visible / ultraviolet absorption spectroscopy (UV), infrared absorption spectroscopy (IR), nuclear magnetic resonance spectroscopy (NMR), and / or mass spectrometry (MS (including GC-MS and / or LS-MS, etc.)).

[0054] When the fullerene-containing layer contains fullerenes, the fullerenes may contain, for example, 90% or more by weight, 95% or more by weight, 97% or more by weight, 98% or more by weight, 99% or more by weight, 99.5% or more by weight, 99.9% or more by weight, or 99.95% or more by weight in the total mass of the fullerene-containing layer.

[0055] Reference Figure 14 This illustrates an example of the latter approach (i.e., the first approach, in which the fullerene layer is a capping layer that partially covers the negative electrode). Figure 14 This is a schematic cross-sectional view showing how a fullerene-containing layer partially covers the negative electrode. In the case where the fullerene-containing layer 2 is composed of particles containing multiple fullerenes (hereinafter also referred to as "fullerene particles") 2a, the multiple fullerene particles 2a are two-dimensionally connected to the surface of the negative electrode 1. Adjacent fullerene particles 2a are in contact with each other. Parts of the multiple fullerene particles 2a separate from each other, and at the separated locations, a portion of the surface of the negative electrode 1 is exposed. Alternatively, the fullerene-containing layer 2 can be formed by stacking fullerene particles 2a in a direction perpendicular to the negative electrode surface. For example, such a fullerene-containing layer 2 can be formed by dropping a dispersion of fullerene particles 2a onto the surface of the negative electrode 1 to form a coating film, and then drying the coating film. The fullerene particles 2a can be dispersed in the dispersion as primary particles or as secondary particles that aggregate to form aggregates.

[0056] In the second approach, the fullerene-containing layer serves as a membrane. In the electrochemical device according to this embodiment, the negative electrode is in contact with the fullerenes through a structure in which a membrane having at least a portion of its surface covered by fullerenes is in contact with the negative electrode. For example, when the membrane has multiple pores and the fullerene-containing layer is composed of multiple fullerene particles, in addition to continuously or partially covering the surface of the membrane as in the first approach, the fullerene particles may sometimes enter or embed into the pores.

[0057] In this embodiment, "improved cycle characteristics and energy density" refers to the improvement in cycle characteristics and energy density in an electrochemical device with a magnesium electrode system having a "negative electrode in contact with a fullerene-containing layer" and an electrolyte containing "magnesium salt," compared to an electrochemical device with the same magnesium electrode system but without a "negative electrode in contact with a fullerene-containing layer." Regarding cycle characteristics, this specifically refers to a relatively higher discharge capacity retention rate during repeated charge-discharge cycles (see reference). Figure 13 In terms of energy density, this specifically refers to a relatively higher discharge voltage (see reference). Figures 10-11 ).

[0058] In this specification, "cycle characteristics" broadly refers to the ability to more effectively suppress the decrease in discharge capacity even with repeated charge and discharge cycles. In a narrower sense, "cycle characteristics" refers to the discharge capacity retention rate obtained through the following cycle tests, and "improved cycle characteristics" means a relatively high discharge capacity retention rate.

[0059] Cyclic test

[0060] The cycle test was conducted in a constant temperature bath at 25°C. Discharge was performed using a constant current of 0.1 mA until a discharge termination voltage of 0.7 V was reached. After a 1-hour pause following discharge, charging began. Charging was performed using a constant current of 0.1 mA until a charging termination voltage of 2.2 V was reached, followed by a 1-hour pause. This charge-discharge cycle was repeated 20 times. Under these conditions, the ratio of the discharged capacity of the battery cell after cycles to the initial discharged capacity was used as the capacity retention rate after cycles.

[0061] In this specification, "energy density" broadly refers to the characteristic that the reduction in discharge voltage (voltage drop) caused by negative electrode overvoltage is more effectively suppressed. In a narrower sense, "energy density" refers to the characteristic based on the discharge voltage obtained through the aforementioned cyclic tests (especially the discharge voltage of the first cycle), and "increased energy density" means that the discharge voltage is relatively high.

[0062] An electrochemical device with a magnesium electrode system, comprising a negative electrode in contact with a fullerene-containing layer and an electrolyte containing a magnesium salt, can improve its cycle characteristics and energy density. This is especially true when the electrochemical device has a sulfur electrode as the positive electrode. That is, the positive electrode of the electrochemical device according to this embodiment is preferably a sulfur electrode. In the case of an electrochemical device having such a magnesium-sulfur electrode pair (hereinafter also referred to as an "electrochemical device with a magnesium-sulfur electrode system" or a "Mg-S battery," etc.), the cycle characteristics and energy density of the electrochemical device according to this embodiment can be further improved. When the cycle characteristics and energy density become higher, the magnesium-sulfur electrode system electrochemical device becomes more adaptable to use in practical environments, and it is easier to realize the desired device. Assuming that the magnesium-sulfur electrode system electrochemical device is a secondary battery, this embodiment has revealed the possibility of a Mg-S battery that is more suitable for practical use.

[0063] Fullerenes are, for example, unsubstituted fullerenes or fullerene derivatives. As unsubstituted fullerenes, for example, those selected from C... 60 (Chemical Formula 1), C 70 C 84 C 90 And C 96 At least one fullerene from the group consisting of [group A]. Fullerenes are selected from C[group B]. 60 C 70 C 84 C 90 And C 96 When at least one fullerene from the group comprising the fullerene is used, the electrochemical device of the magnesium electrode system according to this embodiment is more likely to exhibit higher cycling characteristics and energy density. Fullerene derivatives are fullerenes to which functional groups are added or substituted, on unsubstituted fullerenes. The number of added or substituted functional groups is, for example, an integer from 1 to 10. Such functional groups are, for example, at least one functional group selected from the group consisting of alkyl, alkenyl, cycloalkyl, alkoxy, aryl, amino, hydroxyl, nitro, acyl, and halogen. Among these, unsubstituted fullerenes are preferred, and C14 is more preferred. 60 .

[0064] [Chemical Formula 1]

[0065]

[0066] Fullerenes can be selected individually from the group consisting of unsubstituted fullerenes and fullerene derivatives, or in combination of two or more. When two or more fullerenes are combined, one of the two or more fullerenes can be included as a main component in the fullerene group. Here, in this specification, a main component refers to a component containing 90% or more by weight, 95% or more by weight, 97% or more by weight, 98% or more by weight, 99% or more by weight, 99.5% or more by weight, 99.9% or more by weight, or 99.95% or more by weight in the total content of the fullerenes. For example, in a fullerene group composed of C... 60 C 60 In the case of unsubstituted fullerenes other than those used in the composition, the fullerenes may contain more than 99.5% by weight of C in the fullerene layer content. 60 .

[0067] In the electrochemical device described in this embodiment, the electrolyte is composed of at least a solvent and a magnesium salt contained in the solvent.

[0068] The solvent is, for example, at least one solvent selected from the group consisting of straight-chain ethers, cyclic ethers, and dialkyl sulfones. When the solvent is at least one solvent selected from the group consisting of straight-chain ethers, cyclic ethers, and dialkyl sulfones, the electrochemical device of the magnesium electrode system according to this embodiment is more likely to exhibit higher cycle characteristics and energy density.

[0069] Straight-chain ethers, for example, are those having the general formula:

[0070] [Chemical Formula 2]

[0071]

[0072] [In the general formula, R' and R” are each independently a hydrocarbon group having 1 or more and 10 or less carbon atoms, and they may be the same or different from each other, and n is an integer of 1 or more and 10 or less] representing an ether with an ethyleneoxy structural unit. When the straight-chain ether is an ether having an ethyleneoxy structural unit represented by the above general formula, the electrochemical device of the magnesium electrode system according to this embodiment is more likely to exhibit higher cycle characteristics and energy density.

[0073] The straight-chain ether solvent used in the electrolyte of the magnesium electrode system described in this embodiment contains one or more ethyleneoxy structural units. Here, "ethyleneoxy structural unit" refers to a molecular structural unit (-O-C2H4-) formed by the combination of an ethylene group and an oxygen atom, and such a molecular structural unit is present in the straight-chain ether more than once. For example, in the case containing one ethyleneoxy structural unit, it can be a straight-chain ether such as dimethoxyethane / DME (ethylene glycol dimethyl ether) and / or diethoxyethane / DEE (ethylene glycol diethyl ether).

[0074] In a preferred embodiment, the ethoxy group has one ethoxy group, meaning the straight-chain ether is dimethoxyethane. Additionally, in another preferred embodiment, the straight-chain ether contains two or more molecular structural units (-O-C2H4-). From another perspective, it can be said that the straight-chain ether in the electrolyte of the magnesium electrode system preferably has a structure formed by the dehydration condensation of two or more diol molecules.

[0075] In the above general formula of a straight-chain ether, R' and R" each independently represent a hydrocarbon group. Therefore, R' and R" can be independently aliphatic hydrocarbon groups, aromatic hydrocarbon groups, and / or aromatic aliphatic hydrocarbon groups. Here, "straight-chain ether" in this specification means that at least the ethyleneoxy structural unit is unbranched (i.e., does not have a branched structure). This means that R' and R" in the above general formula of a straight-chain ether do not necessarily have to be straight-chain structures; they can also have branched structures. In a preferred embodiment, the straight-chain ether used in the electrolyte of the magnesium electrode system according to this embodiment is a diol ether in which not only the ethyleneoxy structural unit is unbranched, but also R' and R" are unbranched.

[0076] Preferably, in this embodiment, when the straight-chain ether has an "ethoxyl group" and interacts with the "negative electrode in contact with a fullerene-containing layer," the cycle characteristics and energy density in the electrochemical device of the magnesium electrode system are easily improved. That is, since the solvent of the straight-chain ether having at least an "ethoxyl group" and the "negative electrode in contact with a fullerene-containing layer" coexist in the electrolyte, quite good results can be obtained in terms of cycle characteristics and energy density.

[0077] Furthermore, if the straight-chain ether has "two or more ethyleneoxy structural units," its interaction with the presence of the "negative electrode in contact with a fullerene-containing layer" more readily improves the cycle characteristics and energy density of the electrochemical device in the magnesium electrode system. That is, by coexisting a solvent containing a straight-chain ether with at least "two or more ethyleneoxy structural units" in the electrolyte and the "negative electrode in contact with a fullerene-containing layer," a more significant effect on cycle characteristics and energy density can be obtained. This can be attributed to the effective interaction between the "negative electrode in contact with a fullerene-containing layer" and the straight-chain ether solvent containing magnesium salts and having "two or more ethyleneoxy structural units," which in turn affects the cycle characteristics and energy density of the electrochemical device in the magnesium electrode system.

[0078] The linear ether having two or more ethylene oxide structural units is not particularly limited, and examples include diethylene glycol ethers, triethylene glycol ethers, tetraethylene glycol ethers, pentaethylene glycol ethers, and hexaethylene glycol ethers. Similarly, a linear ether having two or more ethylene oxide structural units can be a heptaethylene glycol ether, octaethylene glycol ether, nonaethylene glycol ether, decaethylene glycol ether, etc., and further, it can be a polyethylene glycol ether having more ethylene oxide structural units.

[0079] In a preferred embodiment of the straight-chain ether, the hydrocarbon group having 1 or more and 10 or less carbon atoms is an aliphatic hydrocarbon group. That is, regarding the straight-chain ether contained in the electrolyte of the magnesium electrode system involved in this embodiment, R' and R" in the above general formula can each be independently an aliphatic hydrocarbon group having 1 or more and 10 or less carbon atoms. The straight-chain ether in the preferred embodiment is not particularly limited, and examples include ethylene glycol ethers, diethylene glycol ethers, triethylene glycol ethers, tetraethylene glycol ethers, pentaethylene glycol ethers, and hexaethylene glycol ethers. Similarly, the straight-chain ether in the preferred embodiment can be heptaethylene glycol ethers, octaethylene glycol ethers, nonaethylene glycol ethers, and decaethylene glycol ethers. Among them, R' and R" in the above general formula are each independently preferably aliphatic hydrocarbon groups having 1 or more and 4 or less carbon atoms (e.g., lower alkyl groups having 1 or more and 4 or less carbon atoms such as methyl, ethyl, n-propyl, isopropyl, and n-butyl).

[0080] (Ethylene glycol ethers)

[0081] Examples of ethylene glycol ethers include: ethylene glycol dimethyl ether, ethylene glycol ethyl methyl ether, ethylene glycol methyl propyl ether, ethylene glycol butyl methyl ether, ethylene glycol methyl pentyl ether, ethylene glycol methyl hexyl ether, ethylene glycol methyl heptyl ether, and ethylene glycol methyl octyl ether.

[0082] Ethylene glycol diethyl ether, ethylene glycol ethyl propyl ether, ethylene glycol butyl ethyl ether, ethylene glycol ethyl pentyl ether, ethylene glycol ethyl hexyl ether, ethylene glycol ethyl heptyl ether, and ethylene glycol ethyl octyl ether;

[0083] Ethylene glycol dipropyl ether, ethylene glycol butylpropyl ether, ethylene glycol propylpentyl ether, ethylene glycol propylhexyl ether, ethylene glycol propylheptyl ether and ethylene glycol propyl octyl ether;

[0084] Ethylene glycol dibutyl ether, ethylene glycol butylpentyl ether, ethylene glycol butylhexyl ether, ethylene glycol butylheptyl ether, and ethylene glycol butyloctyl ether;

[0085] Ethylene glycol dipentyl ether, ethylene glycol hexylpentyl ether, ethylene glycol heptaylpentyl ether, and ethylene glycol octylpentyl ether;

[0086] Ethylene glycol dihexyl ether, ethylene glycol heptylhexyl ether, and ethylene glycol hexyl octyl ether;

[0087] Ethylene glycol diheptyl ether and ethylene glycol heptyl octyl ether; and

[0088] Ethylene glycol dioctyl ether.

[0089] (Diethylene glycol ethers)

[0090] Examples of diethylene glycol ethers include: diethylene glycol dimethyl ether, diethylene glycol ethyl methyl ether, diethylene glycol methyl propyl ether, diethylene glycol butyl methyl ether, diethylene glycol methyl pentyl ether, diethylene glycol methyl hexyl ether, diethylene glycol methyl heptyl ether, and diethylene glycol methyl octyl ether.

[0091] Diethylene glycol diethyl ether, diethylene glycol ethyl propyl ether, diethylene glycol butyl ethyl ether, diethylene glycol ethyl pentyl ether, diethylene glycol ethyl hexyl ether, diethylene glycol ethyl heptyl ether and diethylene glycol ethyl octyl ether;

[0092] Diethylene glycol dipropyl ether, diethylene glycol butylpropyl ether, diethylene glycol propylpentyl ether, diethylene glycol propylhexyl ether, diethylene glycol propylheptyl ether and diethylene glycol propyl octyl ether;

[0093] Diethylene glycol dibutyl ether, diethylene glycol butylpentyl ether, diethylene glycol butylhexyl ether, diethylene glycol butylheptyl ether, diethylene glycol butyl octyl ether;

[0094] Diethylene glycol dipentyl ether, diethylene glycol hexylpentyl ether, diethylene glycol heptylpentyl ether and diethylene glycol octylpentyl ether;

[0095] Diethylene glycol dihexyl ether, diethylene glycol heptylhexyl ether and diethylene glycol hexyloctyl ether;

[0096] Diethylene glycol diheptyl ether, diethylene glycol heptyl octyl ether; and

[0097] Diethylene glycol dioctyl ether.

[0098] (Triethylene glycol ethers)

[0099] Examples of triethylene glycol ethers include: triethylene glycol dimethyl ether, triethylene glycol ethyl methyl ether, triethylene glycol methyl propyl ether, triethylene glycol butyl methyl ether, triethylene glycol methyl pentyl ether, triethylene glycol methyl hexyl ether, triethylene glycol methyl heptyl ether, and triethylene glycol methyl octyl ether.

[0100] Triethylene glycol diethyl ether, triethylene glycol ethyl propyl ether, triethylene glycol butyl ethyl ether, triethylene glycol ethyl pentyl ether, triethylene glycol ethyl hexyl ether, triethylene glycol ethyl heptyl ether, triethylene glycol ethyl octyl ether;

[0101] Triethylene glycol dipropyl ether, triethylene glycol butylpropyl ether, triethylene glycol propylpentyl ether, triethylene glycol propylhexyl ether, triethylene glycol propylheptyl ether and triethylene glycol propyl octyl ether;

[0102] Triethylene glycol dibutyl ether, triethylene glycol butylpentyl ether, triethylene glycol butylhexyl ether, triethylene glycol butylheptyl ether, triethylene glycol butyl octyl ether;

[0103] Triethylene glycol dipentyl ether, triethylene glycol hexylpentyl ether, triethylene glycol heptylpentyl ether, and triethylene glycol octylpentyl ether;

[0104] Triethylene glycol dihexyl ether, triethylene glycol heptylhexyl ether, triethylene glycol hexyl octyl ether;

[0105] Triethylene glycol diheptyl ether and triethylene glycol heptyl octyl ether; and

[0106] Triethylene glycol dioctyl ether.

[0107] (Tetraethylene glycol ethers)

[0108] Examples of tetraethylene glycol ethers include: tetraethylene glycol dimethyl ether, tetraethylene glycol ethyl methyl ether, tetraethylene glycol methyl propyl ether, tetraethylene glycol butyl methyl ether, tetraethylene glycol methyl pentyl ether, tetraethylene glycol methyl hexyl ether, tetraethylene glycol methyl heptyl ether, and tetraethylene glycol methyl octyl ether.

[0109] Tetraethylene glycol diethyl ether, tetraethylene glycol ethyl propyl ether, tetraethylene glycol butyl ethyl ether, tetraethylene glycol ethyl pentyl ether, tetraethylene glycol ethyl hexyl ether, tetraethylene glycol ethyl heptyl ether and tetraethylene glycol ethyl octyl ether;

[0110] Tetraethylene glycol dipropyl ether, tetraethylene glycol butylpropyl ether, tetraethylene glycol propylpentyl ether, tetraethylene glycol propylhexyl ether, tetraethylene glycol propylheptyl ether and tetraethylene glycol propyl octyl ether;

[0111] Tetraethylene glycol dibutyl ether, tetraethylene glycol butylpentyl ether, tetraethylene glycol butylhexyl ether, tetraethylene glycol butylheptyl ether, tetraethylene glycol butyloctyl ether;

[0112] Tetraethylene glycol dipentyl ether, tetraethylene glycol hexylpentyl ether, tetraethylene glycol heptylpentyl ether, and tetraethylene glycol octylpentyl ether;

[0113] Tetraethylene glycol dihexyl ether, tetraethylene glycol heptylhexyl ether, tetraethylene glycol hexyl octyl ether;

[0114] Tetraethylene glycol diheptyl ether and tetraethylene glycol heptyl octyl ether; and

[0115] Tetraethylene glycol dioctyl ether.

[0116] (Pentaethylene glycol ethers)

[0117] Examples of pentaethylene glycol ethers include: pentaethylene glycol dimethyl ether, pentaethylene glycol ethyl methyl ether, pentaethylene glycol methyl propyl ether, pentaethylene glycol butyl methyl ether, pentaethylene glycol methyl pentyl ether, pentaethylene glycol methyl hexyl ether, pentaethylene glycol methyl heptyl ether, and pentaethylene glycol methyl octyl ether.

[0118] Pentaethylene glycol diethyl ether, pentaethylene glycol ethyl propyl ether, pentaethylene glycol butyl ethyl ether, pentaethylene glycol ethyl pentyl ether, pentaethylene glycol ethyl hexyl ether, pentaethylene glycol ethyl heptyl ether, and pentaethylene glycol ethyl octyl ether;

[0119] Pentaethylene glycol dipropyl ether, pentaethylene glycol butylpropyl ether, pentaethylene glycol propylpentyl ether, pentaethylene glycol propylhexyl ether, pentaethylene glycol propylheptyl ether, and pentaethylene glycol propyl octyl ether;

[0120] Pentaethylene glycol dibutyl ether, pentaethylene glycol butylpentyl ether, pentaethylene glycol butylhexyl ether, pentaethylene glycol butylheptyl ether, pentaethylene glycol butyloctyl ether;

[0121] Pentaethylene glycol dipentyl ether, pentaethylene glycol hexylpentyl ether, pentaethylene glycol heptylpentyl ether, and pentaethylene glycol octylpentyl ether;

[0122] Pentaethylene glycol dihexyl ether, pentaethylene glycol heptylhexyl ether, pentaethylene glycol hexyl octyl ether;

[0123] Pentaethylene glycol diheptyl ether and pentaethylene glycol heptyl octyl ether; and

[0124] Pentaethylene glycol dioctyl ether.

[0125] (Hexaethylene glycol ethers)

[0126] Examples of hexaethylene glycol ethers include: hexaethylene glycol dimethyl ether, hexaethylene glycol ethyl methyl ether, hexaethylene glycol methyl propyl ether, hexaethylene glycol butyl methyl ether, hexaethylene glycol methyl pentyl ether, hexaethylene glycol methyl hexyl ether, hexaethylene glycol methyl heptyl ether, and hexaethylene glycol methyl octyl ether.

[0127] Hexaethylene glycol diethyl ether, hexaethylene glycol ethyl propyl ether, hexaethylene glycol butyl ethyl ether, hexaethylene glycol ethyl pentyl ether, hexaethylene glycol ethyl hexyl ether, hexaethylene glycol ethyl heptyl ether, and hexaethylene glycol ethyl octyl ether;

[0128] Hexaethylene glycol dipropyl ether, hexaethylene glycol butylpropyl ether, hexaethylene glycol propylpentyl ether, hexaethylene glycol propylhexyl ether, hexaethylene glycol propylheptyl ether and hexaethylene glycol propyl octyl ether;

[0129] Hexaethylene glycol dibutyl ether, hexaethylene glycol butylpentyl ether, hexaethylene glycol butylhexyl ether, hexaethylene glycol butylheptyl ether, hexaethylene glycol butyloctyl ether;

[0130] Hexaethylene glycol dipentyl ether, hexaethylene glycol hexylpentyl ether, hexaethylene glycol heptylpentyl ether, and hexaethylene glycol octylpentyl ether;

[0131] Hexaethylene glycol dihexyl ether, hexaethylene glycol heptylhexyl ether, hexaethylene glycol hexyloctyl ether;

[0132] Hexaethylene glycol diheptyl ether and hexaethylene glycol heptayl octyl ether; and

[0133] Hexaethylene glycol dioctyl ether.

[0134] It should be noted that the straight-chain ether in the preferred embodiment can also be a heptaethylene glycol ether, an octaethylene glycol ether, a nonaethylene glycol ether, or a decaethylene glycol ether, and more specifically, it can be a polyethylene glycol ether.

[0135] Additionally, cyclic ethers are, for example, tetrahydrofuran. Dialkyl sulfones can be, for example, derived from the general formula:

[0136] R'-SO2-R" indicates that

[0137] [In the general formula, R' and R” are each independently a hydrocarbon group with 1 or more carbon atoms and less than 4 carbon atoms, and they can be the same or different from each other.]

[0138] In a preferred embodiment of the dialkyl sulfone, the hydrocarbon group having 1 or more and 4 or less carbon atoms is an aliphatic hydrocarbon group. That is, regarding the dialkyl sulfone contained in the electrolyte of the electrochemical device according to this embodiment, R' and R" in the above general formula for dialkyl sulfone can each be independently an aliphatic hydrocarbon group (lower alkyl group having 1 or more and 4 or less carbon atoms). There is no particular limitation on the dialkyl sulfone, and for example it can be dimethyl sulfone, methyl ethyl sulfone, methyl n-propyl sulfone, methyl isopropyl sulfone, methyl n-butyl sulfone, methyl isobutyl sulfone, methyl sec-butyl sulfone, methyl tert-butyl sulfone, ethyl methyl sulfone, diethyl sulfone, ethyl n-propyl sulfone, ethyl isopropyl sulfone, ethyl sec-butyl sulfone, ethyl tert-butyl sulfone, di n-propyl sulfone, diisopropyl sulfone, n-propyl n-butyl sulfone, n-butyl ethyl sulfone, isobutyl ethyl sulfone, sec-butyl ethyl sulfone, and di n-butyl sulfone.

[0139] The electrolyte of the magnesium electrode system in this embodiment contains a magnesium salt. The magnesium salt can be one type or a combination of several types. Preferably, the magnesium salt is at least one selected from the group consisting of magnesium halides, magnesium perfluoroalkyl sulfonylimide, and magnesium bis(hexaalkyl)silane. By using such a magnesium salt, the electrochemical device of the magnesium electrode system according to this embodiment more easily exhibits higher cycle characteristics and energy density.

[0140] Such magnesium salts can be produced by the general formula MgX n(Where n is 1 or 2, and X is a monovalent or divalent anion). When X is a halogen (more specifically, F, Cl, Br, and I), the magnesium salt forms a metal halide (magnesium halide). At least one of the following can be listed as a metal halide: magnesium fluoride (MgF₂), magnesium chloride (MgCl₂), magnesium bromide (MgBr₂), and magnesium iodide (MgI₂). Magnesium chloride is preferred as the metal halide. The interaction between magnesium chloride (MgCl₂) and the "negative electrode in contact with the fullerene-containing layer" can promote high cycling characteristics and energy density of the electrochemical device.

[0141] When X has a disilane structure represented by the general formula (R3Si)2N (in which R is a hydrocarbon group with 1 or more carbon atoms and less than 10 carbon atoms), the structure is represented by the general formula MgX. n Magnesium salts represented by (where n is 1 or 2, and X is a monovalent or divalent anion) form magnesium salts with a disilane structure. In the general formula, R is preferably an aliphatic hydrocarbon group with 1 or more but less than 10 carbon atoms, and more preferably a lower alkyl group with 1 or more but less than 4 carbon atoms. Such magnesium salts are preferably magnesium salts of hexaalkyldisilane (magnesium bis(hexaalkyldisilane)2, where R is an alkyl group). The interaction between the "magnesium salt" with such a disilane structure and the "negative electrode in contact with the fullerene-containing layer" can promote high cycling characteristics and energy density of the electrochemical device of the magnesium electrode system.

[0142] When X has an imide (preferably a sulfonamide) as its molecular structure, it is derived from the general formula MgX. n (where n is 1 or 2, and X is a monovalent or divalent anion) represents a magnesium salt that forms an imide metal salt. The imide metal salt is preferably a magnesium salt of a perfluoroalkyl sulfonamide (Mg((R)) f1 SO2)2N)2). In the general formula, R f1The imide metal salt can be a perfluoroalkyl group with 1 or more but less than 10 carbon atoms, a perfluoroalkyl group with 1 or more but less than 8 carbon atoms, a perfluoroalkyl group with 1 or more but less than 6 carbon atoms, a perfluoroalkyl group with 1 or more but less than 4 carbon atoms, a perfluoroalkyl group with 1 or more but less than 3 carbon atoms, or a perfluoroalkyl group with 1 or more but less than 2 carbon atoms. The interaction between such an imide metal salt and the negative electrode in contact with a fullerene-containing layer can promote high cycling characteristics and energy density of the electrochemical device. As an example, the imide metal salt can be magnesium bis(trifluoromethanesulfonyl)imide, i.e., Mg(TFSI)2. This Mg(TFSI)2 readily achieves high cycling characteristics and energy density in the electrochemical device according to this embodiment. In a preferred embodiment, the interaction between Mg(TFSI)2 and the aforementioned halide metal salt (especially magnesium chloride (MgCl2)) and the negative electrode in contact with a fullerene-containing layer can promote high cycling characteristics and energy density of the magnesium electrode system electrochemical device.

[0143] Alternatively, X can be other anions, such as magnesium perchlorate (Mg(ClO4)2), magnesium nitrate (Mg(NO3)2), magnesium sulfate (MgSO4), magnesium acetate (Mg(CH3COO)2), magnesium trifluoroacetate (Mg(CF3COO)2), magnesium tetrafluoroborate (Mg(BF4)2), magnesium tetraphenylborate (Mg(B(C6H5)4)2), magnesium hexafluorophosphate (Mg(PF6)2), magnesium hexafluoroarsenate (Mg(AsF6)2), and magnesium salts of perfluoroalkyl sulfonic acids (Mg(R)). f2 SO3)2)(wherein, R f2 It is at least one magnesium salt in the group consisting of perfluoroalkyl groups.

[0144] In another preferred embodiment, the magnesium salt is a combination of two salts: a halide metal salt and an imide metal salt. The halide metal salt can be, for example, magnesium chloride (MgCl2), and the imide salt can be a magnesium salt of a perfluoroalkyl sulfonyl imide, such as Mg(TFSI)2. MgCl2 and Mg(TFSI)2 are relatively stable Mg salts. Therefore, even with high concentrations of MgCl2 and Mg(TFSI)2 in a straight-chain ether solvent, high safety can be achieved. This provides advantages different from electrolytes using existing AlCl3 and Grignard reagents. Moreover, since MgCl2 and Mg(TFSI)2 have low reactivity, no side reactions other than the electrochemical reaction with sulfur are generated, and higher capacity can be expected. Furthermore, since the overvoltage for magnesium deposition and dissolution is low, the charge-discharge hysteresis is narrower than in previously reported examples, which also promises to achieve high energy density in the device. Furthermore, it enables a very high total concentration of Mg salt, high ionic conductivity, and high-rate characteristics, and also has a lower freezing point and a higher boiling point, thus enabling electrochemical devices with a wide temperature range.

[0145] As magnesium salts, when using a combination of halide and imide salts, their molar amounts can be equal (in a specific example, they can be equimolar). Although not particularly limited, for example, in the combination of MgCl2 and Mg(TFSI)2, the molar ratio of MgCl2:Mg(TFSI)2 can be around 1:0.3 to 1.7, for example, 1:0.4 to 1.6 or 1:0.5 to 1.5, or, depending on the type of straight-chain ether, around 1:0.7 to 1.3, for example, 1:0.85 to 1.25.

[0146] In the electrochemical device according to this embodiment, the electrolyte may also contain fullerenes as additives. In this case, the amount of fullerene added to the electrolyte containing a solvent and a magnesium salt contained in the solvent is preferably small. In this respect, the content of fullerenes in the electrolyte (on a total electrolyte basis) can be less than the content of magnesium salts in the electrolyte (on a total electrolyte basis). In a preferred embodiment, the content of fullerenes in the electrolyte (the amount of fullerenes relative to the total amount of electrolyte) is less than 1 / 2, less than 1 / 5, or less than 1 / 10 of the content of magnesium salts in the electrolyte (the amount of magnesium salts relative to the total amount of electrolyte), etc.

[0147] In other words, the molar concentration of fullerenes based on the electrolyte can be less than the content of magnesium salts based on the electrolyte. Although this is only an example, the content of fullerenes in the electrolyte can be, for example, equivalent to a very small amount added, such as less than 0.5M (overall electrolyte basis), less than 0.1M (overall electrolyte basis), less than 0.05M (overall electrolyte basis), or less than 0.01M (overall electrolyte basis). Even such a small amount can further improve the cycle characteristics and energy density of the electrochemical device of the magnesium electrode system in this embodiment.

[0148] The electrolyte involved in this embodiment is a so-called "magnesium electrode system" electrolyte. Even with such a magnesium electrode system electrolyte, the addition of "fullerenes" can further improve the cycle characteristics, which is extremely useful. This is because it is generally considered difficult to improve cycle characteristics with additives when the Mg coordination structure is very fragile. That is, in this embodiment, although it is a "magnesium electrode system" electrochemical device, the improvement in cycle characteristics and energy density provides a battery utilization approach more suitable for use in real-world environments.

[0149] The electrochemical device according to this embodiment can include the above-described electrolyte and an electrolyte layer made of a polymer compound that holds the electrolyte.

[0150] The polymeric compound can swell in the electrolyte. In this case, the polymeric compound swollen in the electrolyte can be in a gel-like state. Examples of such polymeric compounds include polyacrylonitrile, polyvinylidene fluoride, copolymers of polyvinylidene fluoride and hexafluoropropylene, polytetrafluoroethylene, polyhexafluoropropylene, polyethylene oxide, polypropylene oxide, polyphosphazene, polysiloxane, polyvinyl acetate, polyvinyl alcohol, polymethyl methacrylate, polyacrylic acid, polymethacrylic acid, styrene-butadiene rubber, nitrile-butadiene rubber, polystyrene, and / or polycarbonate. In particular, from the viewpoint of prioritizing electrochemical stability, polyacrylonitrile, polyvinylidene fluoride, polyhexafluoropropylene, or polyethylene oxide can be used. The electrolyte layer can be a solid electrolyte layer.

[0151] The electrochemical device with magnesium electrode system described in this embodiment can be configured as a secondary battery. Figure 1 A conceptual diagram illustrating this situation. As shown in the figure, during charging, magnesium ions (Mg... 2+ Magnesium ions move from the positive electrode 10 through the electrolyte layer 12 to the negative electrode 11, thereby converting electrical energy into chemical energy and storing it. During discharge, magnesium ions return from the negative electrode 11 through the electrolyte layer 12 to the positive electrode 10, thus generating electrical energy.

[0152] When the electrochemical device is a battery (primary or secondary) composed of the aforementioned electrolyte, the battery can be used as a power source or auxiliary power source for devices such as laptops, PDAs (portable information terminals), mobile phones, smartphones, cordless phones (master or slave units), camcorders, digital still cameras, e-books, electronic dictionaries, portable music players, radios, headphones, game consoles, navigation systems, memory cards, pacemakers, hearing aids, power tools, electric shavers, refrigerators, air conditioners, television receivers, stereos, water heaters, microwave ovens, dishwashers, washing machines, dryers, lighting equipment, toys, medical devices, robots, load conditioners, signal lights, railway vehicles, golf carts, electric carts, and / or electric vehicles (including hybrid vehicles). Additionally, it can be used as a power storage source for buildings such as residences or for power generation equipment, or for supplying power to them. In electric vehicles, the conversion device that transforms electricity into driving force is generally an electric motor. Control units (control departments) that perform information processing related to vehicle control include control devices that display the remaining battery level based on information related to the remaining battery level. Additionally, batteries can be used in energy storage devices within so-called smart grids. Such energy storage devices can not only supply electricity but also store electricity by receiving power from other power sources. These other power sources include, for example, thermal power generation, nuclear power generation, hydropower generation, solar cells, wind power generation, geothermal power generation, and / or fuel cells (including biofuel cells).

[0153] The electrochemical device (i.e., secondary battery) according to this embodiment can be applied in a secondary battery, a control unit (or control unit) that performs control related to the secondary battery, and a battery pack having an outer package containing the secondary battery. In this battery pack, the control unit, for example, performs control of charging, discharging, over-discharging, or overcharging related to the secondary battery.

[0154] The electrochemical device (i.e., secondary battery) according to this embodiment can be applied to an electronic device that receives power from the secondary battery.

[0155] The electrochemical device described in this embodiment can also be applied to secondary batteries in electric vehicles, which include a conversion device that receives power from the secondary battery and converts it into driving force for the vehicle, and a control device (or control unit) that performs vehicle control-related information processing based on information related to the secondary battery. In such electric vehicles, the conversion device typically receives power from the secondary battery and drives a motor to generate driving force. The motor can also utilize regenerative energy. Furthermore, the control device (or control unit) performs vehicle control-related information processing, for example, based on the remaining battery capacity of the secondary battery. Such electric vehicles include, for example, electric cars, electric motorcycles, electric bicycles, and railway vehicles, as well as so-called hybrid vehicles.

[0156] The electrochemical device (i.e., secondary battery) according to this embodiment can be applied to power systems configured to receive power from the secondary battery and / or supply power from a power source to the secondary battery. Such a power system can be any power system as long as it generally uses electricity, and also includes simple power devices. Such power systems include, for example, smart grids, home energy management systems (HEMS), and / or vehicles, and can also store electricity.

[0157] The electrochemical device (i.e., secondary battery) according to this embodiment can be applied to a power storage power source configured to be connected to an electronic device having a secondary battery and supplied with power. The application of this power storage power source is not limited; it can be used in virtually any power system or power device, such as a smart grid.

[0158] More detailed information, more specific methods, and other matters concerning the electrochemical device involved in this embodiment have been described in the above-mentioned "electrolyte for the electrochemical device involved in this embodiment," so the description is omitted to avoid repetition.

[0159] Here, the electrochemical device with magnesium electrode system according to this embodiment is provided as a secondary battery in further detail. Hereinafter, this secondary battery will also be referred to as a "magnesium secondary battery".

[0160] The magnesium secondary battery used in the electrochemical device according to this embodiment is not particularly limited to any machinery, equipment, appliance, device, or system (a collection of multiple devices, etc.) that can be used as a power source for driving / operating or as a power storage source for power storage. The magnesium secondary battery used as a power source (e.g., a magnesium-sulfur secondary battery) can be a main power source (the preferred power source) or an auxiliary power source (a power source used in place of the main power source or switched from the main power source). When using a magnesium secondary battery as an auxiliary power source, the main power source is not limited to the magnesium secondary battery.

[0161] Specifically, applications of magnesium secondary batteries (especially magnesium-sulfur secondary batteries) include: camcorders or video recorders, digital still cameras, mobile phones, personal computers, television receivers, various display devices, cordless phones, stereo headphones, music players, portable radios, e-books and / or electronic newspapers, portable information terminals including PDAs, and various electronic and electrical equipment (including portable electronic devices); toys; portable household appliances such as electric shavers; lighting fixtures such as indoor lamps; medical electronic devices such as pacemakers and / or hearing aids; and storage devices. Storage devices such as memory cards; battery packs used as removable power sources for personal computers, etc.; power tools such as electric drills and / or chainsaws; power storage systems and / or home energy servers (home energy storage devices), power supply systems, such as home battery systems that store electricity in advance for emergencies, etc.; energy storage units and / or backup power supplies; electric vehicles such as electric cars, electric motorcycles, electric bicycles and / or Segway (registered trademark); and the drive of electric drive conversion devices (specifically, such as power motors) for aircraft and / or ships, but not limited to these uses.

[0162] Magnesium secondary batteries (especially magnesium-sulfur secondary batteries) are effective in applications such as battery packs, electric vehicles, power storage systems, power supply systems, power tools, electronic devices, and / or electrical equipment. A battery pack is a power source that uses magnesium secondary batteries; it is also known as a battery array. An electric vehicle is a vehicle that operates (e.g., drives) using magnesium secondary batteries as its driving power source, and can also be a car that has a driving source other than a secondary battery (e.g., a hybrid vehicle). A power storage system (e.g., a power supply system) is a system that uses magnesium secondary batteries as a power storage source. For example, in a household power storage system (power supply system), electricity is stored in the magnesium secondary batteries, which act as a power storage source, allowing the use of household electrical products. A power tool is a tool that uses magnesium secondary batteries as a driving power source to move its movable parts (e.g., a drill bit). Electronic devices or electrical equipment are devices that perform various functions using magnesium secondary batteries as a power source (i.e., a power supply source).

[0163] The following describes cylindrical magnesium secondary batteries and flat laminated film magnesium secondary batteries.

[0164] Figure 2This is a schematic cross-sectional view of a cylindrical magnesium secondary battery 100. In the magnesium secondary battery 100, an electrode structure 121 and a pair of insulating plates 112 and 113 are housed inside a generally hollow cylindrical electrode structure housing component 111. The electrode structure 121 is manufactured, for example, by layering a positive electrode 122 and a negative electrode 124 with a separator 126 in between, and then winding the electrode structure. The electrode structure housing component (e.g., a battery can) 111 has a hollow structure with one end closed and the other end open, and is made of iron (Fe) and / or aluminum (Al), etc. The pair of insulating plates 112 and 113 are arranged to sandwich the electrode structure 121 and extend perpendicularly to the winding circumference of the electrode structure 121. The battery cover 114, safety valve mechanism 115, and thermistor element (e.g., PTC element, positive temperature coefficient element) 116 are riveted to the open end of the electrode structure housing 111 via a washer 117, thereby sealing the electrode structure housing 111. The battery cover 114 is made of, for example, the same material as the electrode structure housing 111. The safety valve mechanism 115 and the thermistor element 116 are disposed inside the battery cover 114, and the safety valve mechanism 115 is electrically connected to the battery cover 114 via the thermistor element 116. In the safety valve mechanism 115, when the internal pressure reaches a certain level due to an internal short circuit and / or external heating, the disc plate 115A flips. This disconnects the battery cover 114 from the electrode structure 121. To prevent abnormal heating caused by high current, the resistance of the thermistor element 116 increases with increasing temperature. The washer 117 is made of, for example, an insulating material. Asphalt or similar materials can also be applied to the surface of gasket 117.

[0165] A center pin 118 is inserted into the winding center of the electrode structure 121. However, the center pin 118 may not be inserted into the winding center. A positive electrode lead portion 123 made of a conductive material such as aluminum is connected to the positive electrode 122. Specifically, the positive electrode lead portion 123 is mounted on the positive electrode current collector. A negative electrode lead portion 125 made of a conductive material such as copper is connected to the negative electrode 124. Specifically, the negative electrode lead portion 125 is mounted on the negative electrode current collector. The negative electrode lead portion 125 is soldered to the electrode structure housing member 111 and is electrically connected to the electrode structure housing member 111. The positive electrode lead portion 123 is soldered to the safety valve mechanism 115 and is electrically connected to the battery cover 114. It should be noted that... Figure 2 In the example shown, the negative electrode lead portion 125 is located at one point (the outermost periphery of the wound electrode structure), but there are also cases where it is located at two points (the outermost periphery and the innermost periphery of the wound electrode structure).

[0166] The electrode structure 121 is formed by stacking a positive electrode 122 and a negative electrode 124 separated by a separator 126. The positive electrode 122 has a positive active material layer formed on the positive current collector (more specifically, on both sides of the positive current collector), and the negative electrode 124 has a negative active material layer formed on the negative current collector (more specifically, on both sides of the negative current collector). No positive active material layer is formed in the region of the positive current collector where the positive lead portion 123 is installed, and no negative active material layer is formed in the region of the negative current collector where the negative lead portion 125 is installed.

[0167] Magnesium secondary batteries 100 can be manufactured, for example, based on the following steps.

[0168] First, a positive electrode active material layer is formed on both sides of the positive electrode current collector, and a negative electrode active material layer is formed on both sides of the negative electrode current collector.

[0169] Next, the positive electrode lead portion 123 is installed on the positive electrode current collector using a welding method or the like. Similarly, the negative electrode lead portion 125 is installed on the negative electrode current collector using a welding method or the like. Next, the positive electrode 122 and negative electrode 124 are stacked and wound (more specifically, the electrode structure of positive electrode 122 / separator 126 / negative electrode 124 / separator 126 (i.e., the stacked structure)) through a diaphragm 126 made of microporous polyethylene film to form electrode structure 121. Afterwards, protective tape (not shown) is applied to the outermost periphery. Then, the center pin 118 is inserted into the center of electrode structure 121. Next, while holding electrode structure 121 with a pair of insulating plates 112, 113, electrode structure 121 is housed inside electrode structure housing member 111. In this case, the front end of the positive electrode lead 123 is mounted to the safety valve mechanism 115 using a welding method or similar means, and the front end of the negative electrode lead 125 is mounted to the electrode structure housing member 111. Then, electrolyte is injected under reduced pressure, immersing the diaphragm 126 in the electrolyte. Next, the battery cover 114, the safety valve mechanism 115, and the thermistor element 116 are riveted to the open end of the electrode structure housing member 111 via a gasket 117.

[0170] Next, the planar laminated film type secondary battery will be explained. Figure 3This is a schematic exploded perspective view of the secondary battery. In this secondary battery, an electrode structure 221, essentially the same as described above, is housed inside an outer packaging component 200 made of a laminated film. The electrode structure 221 is manufactured by stacking a positive electrode and a negative electrode layer separated by a separator and an electrolyte layer, and then winding the stacked structure. A positive electrode lead 223 is mounted on the positive electrode, and a negative electrode lead 225 is mounted on the negative electrode. The outermost periphery of the electrode structure 221 is protected by a protective strip. The positive electrode lead 223 and the negative electrode lead 225 protrude from the inside of the outer packaging component 200 in the same direction to the outside. The positive electrode lead 223 is formed of a conductive material such as aluminum. The negative electrode lead 225 is formed of a conductive material such as copper, nickel, and / or stainless steel.

[0171] Outer packaging component 200 is capable of... Figure 3 The outer packaging component 200 is a film folded in the direction of arrow R, and has recesses (e.g., embossing) in a portion therefor to accommodate the electrode structure 221. For example, the outer packaging component 200 is a laminated film in which a welding layer, a metal layer, and a surface protective layer are sequentially stacked. In the manufacturing process of the secondary battery, after folding the outer packaging component 200 with the welding layers facing each other across the electrode structure 221, the outer peripheries of the welding layers are welded together. Alternatively, the outer packaging component 200 may be composed of two separate laminated films bonded together by an adhesive or the like. The welding layer is, for example, a film of polyethylene and / or polypropylene. The metal layer is, for example, an aluminum foil. The surface protective layer is, for example, nylon and / or polyethylene terephthalate. Preferably, the outer packaging component 200 is an aluminum laminated film in which a polyethylene film, an aluminum foil, and a nylon film are sequentially stacked. In addition, the outer packaging component 200 can be a laminated film with other layered structures, a polymer film such as polypropylene, or a metal film. Specifically, it can be composed of a moisture-resistant aluminum laminated film in which nylon film, aluminum foil, and unstretched polypropylene film are layered sequentially from the outside.

[0172] To prevent the intrusion of external gases, a sealing membrane 201 is inserted between the outer packaging component 200 and the positive electrode lead portion 223, and between the outer packaging component 200 and the negative electrode lead portion 225. The sealing membrane 201 may be made of a material that has sealing properties for the positive electrode lead portion 223 and the negative electrode lead portion 225, such as polyolefin resin, and more specifically, it may be made of polyolefin resins such as polyethylene, polypropylene, modified polyethylene, or modified polypropylene.

[0173] The foregoing description primarily considers secondary batteries, but this disclosure also applies to other electrochemical devices, such as capacitors, air batteries, and fuel cells. This will be explained below.

[0174] like Figure 4As shown in the schematic cross-sectional view, the electrochemical device according to this embodiment can be provided as a capacitor. In the capacitor, the positive electrode 31 and the negative electrode 32 are disposed opposite each other, separated by a membrane 33 impregnated with electrolyte. It should be noted that the gel electrolyte membrane impregnated with the electrolyte according to this embodiment can be disposed on the surface of at least one of the membrane 33, the positive electrode 31, and the negative electrode 32. Reference numerals 35 and 36 indicate current collectors, and reference numeral 37 indicates a gasket.

[0175] Or, such as Figure 5 As shown in the conceptual diagram, the electrochemical device involved in this embodiment can also be provided as an air battery. This air battery, for example, comprises the following components: an oxygen-selective permeable membrane 47 that makes it difficult for water vapor to pass through while selectively allowing oxygen to pass through; an air-side current collector 44 made of a conductive porous material; a porous diffusion layer 46 disposed between the air-side current collector 44 and the porous positive electrode 41, made of a conductive material; a porous positive electrode 41 containing a conductive material and a catalyst material; a separator and an electrolyte (or a solid electrolyte containing an electrolyte) 43 that makes it difficult for water vapor to pass through; a negative electrode 42 for magnesium ion insertion / extraction; a negative-side current collector 45; and an outer casing 48 that houses these layers.

[0176] Oxygen 52 from air (e.g., atmosphere) 51 selectively permeates through the oxygen selective permeation membrane 47, diffuses through the air-side current collector 44 (made of porous material), and is supplied to the porous positive electrode 41 via the diffusion layer 46. While the propagation of oxygen through the oxygen selective permeation membrane 47 is partially blocked by the air-side current collector 44, oxygen passing through the air-side current collector 44 diffuses and spreads through the diffusion layer 46, effectively reaching the entire porous positive electrode 41. The supply of oxygen to the entire surface of the porous positive electrode 41 is not hindered by the air-side current collector 44. Furthermore, because the oxygen selective permeation membrane 47 suppresses the permeation of water vapor, degradation caused by moisture in the air is reduced. Since oxygen is effectively supplied to the entire porous positive electrode 41, battery output is improved, enabling stable long-term use.

[0177] Or, such as Figure 6As shown in the conceptual diagram, the electrochemical device involved in this embodiment can also be provided as a fuel cell. The fuel cell, for example, comprises a positive electrode 61, a positive electrode electrolyte 62, a positive electrode electrolyte delivery pump 63, a fuel flow path 64, a positive electrode electrolyte storage container 65, a negative electrode 71, a negative electrode electrolyte 72, a negative electrode electrolyte delivery pump 73, a fuel flow path 74, a negative electrode electrolyte storage container 75, and an ion exchange membrane 66. In the fuel flow path 64, the positive electrode electrolyte 62 flows continuously or intermittently (circulates) via the positive electrode electrolyte storage container 65 and the positive electrode electrolyte delivery pump 63. In the fuel flow path 74, the negative electrode electrolyte 72 flows continuously or intermittently or circulates via the negative electrode electrolyte storage container 75 and the negative electrode electrolyte delivery pump 73, generating electricity between the positive electrode 61 and the negative electrode 71. As the positive electrode electrolyte 62, an electrolyte in which a positive electrode active material has been added can be used, as the electrolyte in this embodiment; and as the negative electrode electrolyte 72, an electrolyte in which a negative electrode active material has been added can be used.

[0178] It should be noted that, regarding the negative electrode in the electrochemical device, besides using Mg metal plates, it can also be manufactured using the following methods. For example, a Mg electrolyte (Mg-EnPS) containing MgCl2 and EnPS (ethyl n-propyl sulfone) can be prepared. Using this Mg electrolyte, Mg metal is deposited on a Cu foil using an electrolytic plating method, forming a Mg coating on the Cu foil as the negative electrode active material layer. Furthermore, XPS analysis of the surface of the Mg coating obtained by this method shows the presence of Mg, C, O, S, and Cl on the surface. Additionally, the Mg-originating peaks observed in the surface analysis did not split; a single Mg-originating peak was observed in the range of 40 eV to 60 eV. Moreover, by Ar sputtering, the surface of the Mg coating was drilled approximately 200 nm deep. XPS analysis of the surface showed that the position and shape of the Mg-originating peaks after Ar sputtering remained unchanged compared to those before Ar sputtering.

[0179] The electrochemical device involved in this embodiment, especially as referred to Figures 1-3 As explained, it can be used as a magnesium secondary battery. The following provides more detailed explanations of several application examples of this magnesium secondary battery. It should be noted that the structures of the application examples described below are only one example, and the structures can be appropriately modified.

[0180] Magnesium secondary batteries can be used in battery packs. These packs are simplified versions of magnesium secondary batteries (so-called pouch cells), used in devices such as smartphones. Alternatively, or based on this, battery arrays can consist of six magnesium secondary batteries connected in a 2-in-parallel-3-in-series configuration. It should be noted that the magnesium secondary batteries can be connected in series, parallel, or a combination of both.

[0181] Figure 7 This is a block diagram illustrating an example of the circuit structure when the magnesium secondary battery according to this embodiment is applied to a battery pack. The battery pack includes a battery cell (e.g., battery pack) 1001, an outer packaging component, a switch unit 1021, a current sensing resistor 1014, a temperature sensing element 1016, and a control unit 1010. The switch unit 1021 includes a charging control switch 1022 and a discharging control switch 1024. Furthermore, the battery pack includes a positive terminal 1031 and a negative terminal 1032. During charging, the positive terminal 1031 and the negative terminal 1032 are connected to the positive and negative terminals of the charger, respectively, for charging. Additionally, when using an electronic device, the positive terminal 1031 and the negative terminal 1032 are connected to the positive and negative terminals of the electronic device, respectively, for discharging.

[0182] The battery unit 1001 is configured by connecting multiple magnesium secondary batteries 1002 of this disclosure in series and / or parallel. It should be noted that... Figure 7 The diagram shows a configuration where six magnesium secondary batteries 1002 are connected in a 2-in-parallel, 3-in-series (2P3S) configuration. However, any other connection method is possible, such as p in parallel and q in series (where p and q are integers).

[0183] The switching unit 1021 includes a charging control switch 1022, a diode 1023, a discharging control switch 1024, and a diode 1025, and is controlled by the control unit 1010. Diode 1023 has the opposite polarity to the charging current flowing from the positive terminal 1031 to the battery cell 1001, and the positive polarity to the discharging current flowing from the negative terminal 1032 to the battery cell 1001. Diode 1025 has the positive polarity to the charging current and the opposite polarity to the discharging current. It should be noted that in this example, the switching unit is provided on the positive (+) side, but it could also be provided on the negative (-) side. The charging control switch 1022, controlled by the control unit 1010, is closed when the battery voltage reaches the overcharge detection voltage, preventing the charging current from flowing through the current path of the battery cell 1001. After the charging control switch 1022 is closed, only discharging can occur through the diode 1023. Furthermore, controlled by the control unit 1010, the switch becomes closed when a large current flows during charging, thereby blocking the charging current flowing through the current path of the battery cell 1001. The discharge control switch 1024, controlled by the control unit 1010, becomes closed when the battery voltage reaches the over-discharge detection voltage, preventing the discharge current from flowing through the current path of the battery cell 1001. After the discharge control switch 1024 becomes closed, charging can only occur through the diode 1025. Additionally, controlled by the control unit 1010, the switch becomes closed when a large current flows during discharging, thereby blocking the discharge current flowing through the current path of the battery cell 1001.

[0184] The temperature sensing element 1016, for example, is a thermistor, and is disposed near the battery cell 1001. The temperature sensing unit 1015 uses the temperature sensing element 1016 to measure the temperature of the battery cell 1001 and sends the measurement result to the control unit 1010. The voltage sensing unit 1012 measures the voltage of the battery cell 1001 and the voltage of each magnesium secondary cell 1002 constituting the battery cell 1001, performs A / D conversion on the measurement results, and sends them to the control unit 1010. The current measuring unit 1013 uses the current sensing resistor 1014 to measure the current and sends the measurement result to the control unit 1010.

[0185] The switch control unit 1020 controls the charging control switch 1022 and the discharging control switch 1024 of the switch unit 1021 based on the voltage and current supplied from the voltage detection unit 1012 and the current measurement unit 1013. When any voltage of the magnesium secondary battery 1002 falls below the overcharge detection voltage or over-discharge detection voltage, and / or when a large current flows rapidly, the switch control unit 1020 sends a control signal to the switch unit 1021 to prevent overcharging, over-discharging, and overcurrent charging / discharging. The charging control switch 1022 and the discharging control switch 1024 can be constructed, for example, by semiconductor switches such as MOSFETs. In this case, diodes 1023 and 1025 are constructed using the parasitic diodes of the MOSFET. When using a p-channel FET as the MOSFET, the switch control unit 1020 provides control signals DO and CO to the gates of the charging control switch 1022 and the discharging control switch 1024, respectively. The charging control switch 1022 and the discharging control switch 1024 are turned on by a gate potential that is a predetermined value lower than the source potential. That is, during normal charging and discharging operations, the control signals CO and DO are set to a low level, turning on the charging control switch 1022 and the discharging control switch 1024. Conversely, for example, during overcharging or over-discharging, the control signals CO and DO are set to a high level, turning on the charging control switch 1022 and the discharging control switch 1024.

[0186] The memory 1011 is configured, for example, as an EPROM (Erasable Programmable Read-Only Memory), which is a non-volatile memory. The memory 1011 stores in advance values ​​calculated by the control unit 1010 and / or internal resistance values ​​of each magnesium secondary battery 1002 in its initial state, measured during the manufacturing process. Furthermore, it can be rewritten as needed. Additionally, by pre-storing the full charge capacity of the magnesium secondary battery 1002, the remaining capacity can be calculated, for example, together with the control unit 1010.

[0187] In the temperature detection unit 1015, the temperature is measured using the temperature detection element 1016, and charge and discharge control is performed when abnormal heating occurs. In addition, corrections are made in the calculation of the remaining capacity.

[0188] Next, the application of magnesium secondary batteries in electric vehicles will be explained. Figure 8A represents a block diagram of the structure of an electric vehicle, such as a hybrid electric vehicle, as an example of an electric vehicle. The electric vehicle, for example, includes within a metal housing 2000 a control unit 2001, various sensors 2002, a power supply 2003, an engine 2010, a generator 2011, inverters 2012 and 2013, a drive motor 2014, a differential 2015, a transmission 2016, and a clutch 2017. Furthermore, the electric vehicle, for example, includes a front-wheel drive axle 2021, front wheels 2022, a rear-wheel drive axle 2023, and rear wheels 2024 connected to the differential 2015 and / or the transmission 2016.

[0189] Electric vehicles can be driven by either an engine 2010 or a motor 2014. The engine 2010 is the primary power source, such as a gasoline engine. When the engine 2010 is used as the power source, its driving force (e.g., rotational force) is transmitted to the front wheel 2022 or the rear wheel 2024 via, for example, a differential 2015 (which serves as the drive unit), a transmission 2016, and a clutch 2017. The rotational force of the engine 2010 is also transmitted to a generator 2011, which generates alternating current (AC) electricity. This AC electricity is then converted to direct current (DC) electricity via an inverter 2013 and stored in a power source 2003. On the other hand, when the motor 2014 (which serves as the conversion unit) is used as the power source, the electricity supplied from the power source 2003 (e.g., DC electricity) is converted to AC electricity via an inverter 2012, and the AC electricity is used to drive the motor 2014. The driving force (e.g., rotational force) converted from electricity by the motor 2014 is transmitted to the front wheel 2022 or the rear wheel 2024 via, for example, the differential device 2015, the transmission 2016, and the clutch 2017, which are driving units.

[0190] When the electric vehicle decelerates via the braking mechanism (not shown), the resistance during deceleration is transmitted as rotational force to the motor 2014, which can use this rotational force to generate alternating current (AC) power. The AC power is converted into direct current (DC) power via the inverter 2012, and the regenerated DC power is stored in the power supply 2003.

[0191] The control unit 2001 controls the overall operation of the electric vehicle and may include, for example, a CPU. The power supply 2003 may include one or more magnesium secondary batteries (not shown). The power supply 2003 may also be configured to connect to an external power source and store electricity by receiving power from the external source. Various sensors 2002 are used, for example, to control the rotational speed of the engine 2010 and the opening degree of the throttle valve (not shown). These sensors 2002 may include, for example, a speed sensor, an acceleration sensor, and / or an engine speed sensor.

[0192] It should be noted that the electric vehicle is a hybrid vehicle, but an electric vehicle can also be a vehicle that does not use an engine 2010 but only uses a power source 2003 and an electric motor 2014 to operate (e.g., an electric car).

[0193] Next, the application of magnesium secondary batteries in power storage systems (such as power supply systems) will be explained. Figure 8 B is a block diagram representing the structure of an energy storage system (e.g., an energy supply system). An energy storage system, for example, includes a control unit 3001, a power supply 3002, a smart meter 3003, and a power hub 3004 inside a building 3000, such as a residential or commercial building.

[0194] Power source 3002 is connected, for example, to electrical equipment (e.g., electronic equipment) 3010 installed inside the house 3000, and can also be connected to an electric vehicle 3011 parked outside the house 3000. Additionally, power source 3002 is connected, for example, to a standby generator 3021 installed in the house 3000 via a power hub 3004, and can also be connected to an external centralized power system 3022 via a smart meter 3003 and the power hub 3004. Electrical equipment (e.g., electronic equipment) 3010 includes, for example, one or more household appliances. Examples of household appliances include, for example, refrigerators, air conditioners, television receivers, and / or water heaters. Standby generator 3021 is, for example, a solar generator and / or a wind turbine. Electric vehicle 3011 includes, for example, electric cars, hybrid vehicles, electric motorcycles, electric bicycles, and / or Segway (registered trademark). As a centralized power system 3022, commercial power sources, power generation devices, transmission networks and / or smart grids (such as next-generation transmission networks) can be listed. In addition, thermal power plants, nuclear power plants, hydropower plants and / or wind power plants can also be listed. As for the power generation devices provided by the centralized power system 3022, various solar cells, fuel cells, wind power generation devices, micro-hydropower generation devices and / or geothermal power generation devices can be listed, but are not limited to these.

[0195] The control unit 3001 controls the operation of the entire power storage system (including the operating status of the power supply 3002), and may include, for example, a CPU. The power supply 3002 may contain one or more magnesium secondary batteries (not shown) according to the present invention. The smart meter 3003 is, for example, a network-compatible power meter installed in the house 3000 of the electricity demander, and is capable of communicating with the electricity supplier. Furthermore, the smart meter 3003, for example, while communicating with the outside world, controls the demand / supply balance within the house 3000, thereby enabling an efficient and stable energy supply.

[0196] In this power storage system, for example, power is stored in power source 3002 from a centralized power system 3022, which serves as an external power source, via a smart meter 3003 and a power hub 3004, and power is also stored in power source 3002 from a stand-alone generator 3021, which serves as an independent power source, via the power hub 3004. Since the power stored in power source 3002 is supplied to electrical equipment (e.g., electronic equipment) 3010 and electric vehicle 3011 according to the instructions of control unit 3001, the electrical equipment (e.g., electronic equipment) 3010 can operate, and the electric vehicle 3011 can be charged. In other words, the power storage system is a system capable of storing and supplying power within house 3000 using power source 3002.

[0197] The electricity stored in the power source 3002 can be used at will. Therefore, for example, electricity can be stored from the centralized power system 3022 to the power source 3002 at night when electricity prices are cheap, and the electricity stored in the power source 3002 can be used during the day when electricity prices are high.

[0198] The power storage system described above can be installed in one household (e.g., a family) or in multiple households (e.g., multiple families).

[0199] Next, the application of magnesium secondary batteries in power tools will be explained. Figure 8 C is a block diagram representing the structure of a power tool. The power tool, for example, is an electric drill. Inside the tool body 4000, made of a plastic material or similar material, there is a control unit 4001 and a power source 4002. A drill bit 4003, serving as a movable part, is rotatably mounted on the tool body 4000. The control unit 4001 controls the overall operation of the power tool (including the operating state of the power source 4002) and may include, for example, a CPU. The power source 4002 may contain one or more magnesium secondary batteries (not shown). In response to the operation of an operating switch (not shown), the control unit 4001 supplies power from the power source 4002 to the drill bit 4003.

[0200] The embodiments of the present invention have been described above, but only typical examples have been illustrated. Therefore, the present invention is not limited thereto, and those skilled in the art will readily understand that various approaches can be considered without changing the spirit of the present invention. For example, the present invention can be modified by design without departing from the spirit of the present invention, and features described in the various embodiments can be combined.

[0201] For example, the composition of the electrolyte, the raw materials used in its manufacture, the manufacturing method, the manufacturing conditions, the characteristics of the electrolyte, and the structure of the electrochemical device and battery described above are examples and are not limited thereto, and can be appropriately modified. The electrolyte involved in this embodiment can be mixed with organic polymers (e.g., polyethylene oxide, polyacrylonitrile, and / or polyvinylidene fluoride (PVdF)) for use as a gel electrolyte.

[0202] The effects described in this manual are merely examples and are not necessarily limited to these effects. In addition, there may be additional effects.

[0203] In the electrochemical device according to this embodiment, the electrolyte is composed of a solvent and a magnesium salt contained in the solvent. However, during the preparation, storage and / or use of the electrolyte, the presence of unavoidable or accidental contamination of components (e.g., trace or extremely trace components that can be identified as trace or micro-scale components by those skilled in the art) is permissible.

[0204] Example

[0205] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples.

[0206] To confirm the effectiveness of the present invention, the following empirical experiments were conducted. Specifically, empirical experiments were conducted to demonstrate whether contact between a magnesium-containing electrode and a fullerene-containing layer helps improve the energy density and cycle characteristics of the electrochemical device.

[0207] [Energy Density]

[0208] (Example 1)

[0209] As an electrochemical device, a magnesium-sulfur secondary battery with the following specifications was fabricated.

[0210] (Specifications for magnesium-sulfur secondary batteries)

[0211] ● Negative electrode: Electrode containing magnesium ( And a 200μm thick Mg plate (99.9% purity, manufactured by Rikazai Corporation), the Mg plate being covered with fullerene)

[0212] ● Positive electrode: Sulfur electrode (This electrode contains 10% by weight of S8 sulfur manufactured by Wako Pure Chemical Industries, Ltd., product number 197-17892; as a conductive additive, it contains 65% by weight of Ketjen Black (KB) manufactured by Lion Corporation, product number ECP600JD; as a binder, it contains 25% by weight of polytetrafluoroethylene (PTFE) manufactured by Asahi Glass Co., Ltd., product number CD-1E; as a current collector, it contains nickel) )

[0213] ●Separator: Glass fiber (Advantec glass fiber, product number GC50)

[0214] ●Electrolyte

[0215] Magnesium salts: Halide metal salts (MgCl2 (acid anhydride): manufactured by Sigma Aldrich, product number 449172, 0.8M) and imide metal salts (Mg(TFSI)2: manufactured by Toyama Pharmaceutical Co., Ltd., product number MGTFSI, 0.8M)

[0216] • Straight-chain ether solvent: Diethylene glycol dimethyl ether (dimethoxyethane) (ultra-dehydrated product), (manufactured by Toyama Pharmaceutical Co., Ltd., product number G2)

[0217] • "Fullerenes": C 60 Fullerene 0.01M (manufactured by Sigma Aldrich, product number 379646)

[0218] ● Rechargeable battery type: CR2016 coin cell battery

[0219] Figure 9 This is a schematic diagram showing the unfolded state of the battery being manufactured. Regarding the positive electrode 23, 10% by mass of sulfur (S8), 60% by mass of Ketjen black as a conductive additive, and 30% by mass of polytetrafluoroethylene (PTFE) as a binder were mixed using an agate mortar. Then, while acclimating it with acetone, it was rolled approximately 10 times using a roller press. Afterward, it was dried under vacuum at 70°C for 12 hours. This yields positive electrode 23. A nickel mesh is used as a current collector and mounted on the positive electrode.

[0220] A fullerene suspension was prepared by dispersing fullerenes in toluene. The fullerene suspension was then dropped onto a Mg plate to form a coated film. By drying the coated film, a fullerene-containing layer was formed on the Mg plate. This created a negative electrode covered by a fullerene-containing layer. Observation of the Mg plate surface using an optical microscope confirmed that the surface of the Mg plate was discontinuously covered by the fullerene-containing layer.

[0221] A gasket 22 is placed on the coin battery canister 21, followed by the sequential layering of a positive electrode 23 made of sulfur, a glass fiber separator 24, a negative electrode 25 made of a Mg plate with a diameter of 15 mm and a thickness of 200 μm, a spacer 26 made of a stainless steel plate with a thickness of 0.5 mm, and a coin battery cover 27. The coin battery canister 21 is then riveted together to seal it. The spacer 26 is pre-spot-welded to the coin battery cover 27. The electrolyte is used in the form contained within the separator 24 of the coin battery 20.

[0222] The battery was charged and discharged under the following conditions.

[0223] (Charging and discharging conditions)

[0224] Discharge conditions: CC discharge 0.1mA / 0.7V cutoff

[0225] Charging conditions: CC charging 0.1mA / 2.2V cutoff

[0226] Temperature: 25℃

[0227] (Example 2)

[0228] Except that a Mg plate (not covered by a fullerene layer) was used instead of the "Mg plate covered by a fullerene layer" in Example 1, and a "membrane containing fullerene" was used instead of "membrane", a magnesium-sulfur secondary battery was made in the same manner as in Example 1, and the same charge and discharge process was performed as in Example 1.

[0229] It should be noted that the fullerene-containing separator was prepared by dropping the fullerene suspension prepared in Example 1 onto one side of a planar separator and then drying it. Observation of the prepared separator using an optical microscope confirmed that the surface of the separator was discontinuously covered by a fullerene-containing layer. In the fabrication of the coin cell, the separator is stacked on the negative electrode with the side containing the fullerene-like layer in contact with the negative electrode.

[0230] (Comparative Example 1)

[0231] Except that a Mg plate (not covered by a fullerene layer) is used instead of the "Mg plate covered by a fullerene layer" in Example 1, and a sulfur electrode covered by a fullerene layer is used instead of the sulfur electrode (not covered by a fullerene layer), a magnesium-sulfur secondary battery is fabricated in the same manner as in Example 1, and the same charge and discharge process is performed as in Example 1.

[0232] It should be noted that,

[0233] (result)

[0234] The results are as follows Figures 10-12 As shown. Figures 10-12 The figures represent the charge-discharge curves for Examples 1, 2, and Comparative Example 1, respectively. The numbers appended to the charge-discharge curves indicate the cycle number. It can be seen that the discharge curves for the first cycle (one cycle) of Examples 1-2 are larger than the discharge curve of Comparative Example 1. That is, the discharge voltages of Examples 1-2 are higher than the discharge voltage of Comparative Example 1.

[0235] The results above show that, when the fullerene-containing layer is used as a separator, and when it is used as a capping layer covering the negative electrode, contacting the negative electrode with the fullerene-containing layer can suppress the voltage drop caused by the negative electrode overvoltage during the initial discharge of the magnesium-sulfur secondary battery (electrochemical device), thereby increasing the energy density. This contributes to electrochemical devices with high energy density.

[0236] [Cyclic Characteristics]

[0237] (Example 3)

[0238] The relationship between specific capacity and cycle number was obtained from the charge-discharge curves obtained in Example 1. Figure 13 (The attenuation curve is represented by the solid line).

[0239] (Comparative Example 2)

[0240] Except that a Mg plate (not covered by a fullerene layer) was used instead of the "Mg plate covered by a fullerene layer" in Example 3, a magnesium-sulfur secondary battery was fabricated in the same manner as in Example 3, and subjected to the same charge-discharge process. The relationship between specific capacity and cycle number was obtained from the resulting charge-discharge curves (from...). Figure 13 The dashed line represents the attenuation curve.

[0241] It should be noted that the fullerene suspension was prepared in the same manner as in Example 1. The fullerene suspension was dropped onto the sulfur electrode to form a coating film. By drying the coating film, a fullerene-containing layer was formed on the sulfur electrode (positive electrode). Thus, a positive electrode covered with a fullerene-containing layer was fabricated. Observation of the surface of the sulfur electrode using an optical microscope confirmed that the surface of the sulfur electrode was discontinuously covered by the fullerene-containing layer.

[0242] (result)

[0243] The results are as follows Figure 13 As shown. Figure 13 The solid and dashed lines in the figure represent the decay curves of Example 3 and Comparative Example 2, respectively. It can be seen that the decay curve of Example 3 decays slowly with increasing cycle number compared to the decay curve of Comparative Example 2. The ratio of the specific capacity at ten discharge cycles to the specific capacity at the first discharge cycle (discharge capacity retention rate) is 65% in Example 3 and 50% in Comparative Example 2. It can be seen that the discharge capacity retention rate of Example 3 is 15% higher than that of Comparative Example 2.

[0244] The results above show that, when the fullerene-containing layer is used as a separator, and when it is used as a capping layer covering the negative electrode, contacting the negative electrode with the fullerene-containing layer can suppress the decrease in discharge capacity caused by cycling in a magnesium-sulfur secondary battery (electrochemical device) and improve cycle characteristics. This contributes to extending the lifespan of the electrochemical device.

[0245] Industrial availability

[0246] The electrochemical device of the present invention can be used in various fields to extract energy using electrochemical reactions. Although only an example, the electrochemical device of the present invention can be used not only as a secondary battery, but also as a capacitor, an air battery, and a fuel cell, among other electrochemical devices.

[0247] Explanation of reference numerals in the attached figures

[0248] 1: Negative electrode; 2: Fullerene-containing layer; 2a: Fullerene particles; 10: Positive electrode; 11: Negative electrode; 12: Electrolyte layer; 20: Coin cell; 21: Coin cell canister; 22: Gasket; 23: Positive electrode; 24: Separator; 25: Negative electrode; 26: Spacer; 27: Coin cell cover; 31: Positive electrode; 32: Negative electrode; 33: Separator; 35, 36: Current collector; 37: Gasket; 41: Porous positive electrode; 42: Negative electrode; 43: Separator and electrolyte; 44: Air-side current collector; 45: Negative-side current collector; 46: Diffusion layer; 47: Oxygen-selective permeable membrane; 48: Outer packaging; 51: Air (atmosphere); 52: Oxygen; 61: Positive electrode; 62: Electrolyte for positive electrode; 63: Electrolyte delivery pump for positive electrode. ; 64: Fuel flow path; 65: Electrolyte storage container for positive electrode; 71: Negative electrode; 72: Electrolyte for negative electrode; 73: Electrolyte transfer pump for negative electrode; 74: Fuel flow path; 75: Electrolyte storage container for negative electrode; 66: Ion exchange membrane; 100: Magnesium secondary battery; 111: Electrode structure housing (battery can); 112, 113: Insulating plate; 114: Battery cover; 115: Safety valve mechanism; 115A: Disc plate; 116: Thermistor element (PTC element); 117: Gasket; 118: Center pin; 121: Electrode structure; 122: Positive electrode; 123: Positive electrode lead; 124: Negative electrode; 125: Negative electrode lead; 126: Separator; 200: Outer packaging component; 201: Sealing 1001: Electrode structure; 222: Positive lead; 223: Negative lead; 1001: Battery cell (battery pack); 1002: Magnesium secondary battery; 1010: Control unit; 1011: Memory; 1012: Voltage detection unit; 1013: Current measurement unit; 1014: Current detection resistor; 1015: Temperature detection unit; 1016: Temperature detection element; 1020: Switch control unit; 1021: Switch unit; 1022: Charging control switch; 1024: Discharging control switch; 1023, 1025: Diodes; 1031: Positive terminal; 1032: Negative terminal; CO, DO: Control signals; 2000: Housing; 2001: Control unit; 2002: Various sensors 2003: Power supply; 2010: Engine; 2011: Generator; 2012, 2013: Inverter; 2014: Drive motor; 2015: Differential device; 2016: Gearbox; 2017: Clutch; 2021: Front drive shaft; 2022: Front wheel; 2023: Rear drive shaft; 2024: Rear wheel; 3000: Building; 3001: Control unit; 3002: Power supply; 3003: Smart meter; 3004: Power hub; 3010: Electrical equipment (electronic equipment); 3011: Electric vehicle; 3021: Standby generator; 3022: Centralized power system; 4000: Tool body; 4001: Control unit; 4002: Power supply; 4003: Drill bit.

Claims

1. An electrochemical device, It comprises a negative electrode, a positive electrode, a membrane disposed between the negative electrode and the positive electrode, and an electrolyte filling the space between the negative electrode, the positive electrode and the membrane. The negative electrode is a magnesium-containing electrode. The electrolyte is composed of a solvent and a magnesium salt contained in the solvent. The negative electrode is in contact with a fullerene-containing layer. The fullerene-containing layer continuously or partially covers the surface of the separator or the surface of the negative electrode.

2. The electrochemical device according to claim 1, wherein, The fullerene-containing layer is a solid.

3. The electrochemical device according to claim 1 or 2, wherein, The fullerene-containing layer comprises particles containing the fullerenes. At least a portion of the particles containing the fullerenes are stacked on the surface of the negative electrode.

4. The electrochemical device according to claim 1 or 2, wherein, The fullerenes are selected from C. 60 C 70 C 84 C 90 And C 96 At least one fullerene from the group comprising the group.

5. The electrochemical device according to claim 1 or 2, wherein, The magnesium salt is at least one selected from the group consisting of magnesium halides, magnesium perfluoroalkyl sulfonylimide, and magnesium dihexyldisilane.

6. The electrochemical device according to claim 1 or 2, wherein, The solvent is at least one solvent selected from the group consisting of straight-chain ethers, cyclic ethers, and dialkyl sulfones.

7. The electrochemical device according to claim 6, wherein, The straight-chain ether is an ether having an ethyleneoxy structural unit, represented by the following general formula. In the general formula, R' and R” are each independently a hydrocarbon group with 1 or more carbon atoms and less than 10, and they may be the same or different from each other, and n is an integer of 1 or more and less than 10.

8. The electrochemical device according to claim 1 or 2, wherein, The positive electrode is a sulfur electrode containing sulfur.

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