Magnesium secondary battery and non-aqueous electrolyte for magnesium secondary battery

Abstract

The present disclosure provides a novel non-aqueous electrolyte for a magnesium secondary battery, and a magnesium secondary battery using the same. The non-aqueous electrolyte, for a magnesium secondary battery, according to the present disclosure contains a non-aqueous solvent, a magnesium salt, and an organoaluminum ate complex salt represented by formula (1) below. In formula (1), R1, R2, R3, and R4 are each independently (i) an alkyl group or (ii) a functional-group-comprising alkyl group.

Description

Technical Field

[0001] The present disclosure relates to a magnesium secondary battery and a non-aqueous electrolyte for a magnesium secondary battery.

Background Art

[0002] In recent years, the development of magnesium secondary batteries has been expected.

[0003] Patent Document 1 describes an electrolyte used in a magnesium secondary battery, which contains a magnesium salt and a cyclic acid anhydride.

[0004] Non-Patent Document 1 describes an alkylated aluminum complex as an electrolyte used in a magnesium secondary battery.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Non-Patent Documents

[0006]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] The present disclosure provides a novel non-aqueous electrolyte for a magnesium secondary battery. The present disclosure further provides a magnesium secondary battery using the non-aqueous electrolyte.

Means for Solving the Problems

[0008] The present disclosure is a non-aqueous solvent, a magnesium salt, An organoaluminum art complex salt represented by the following formula (1), and A non-aqueous electrolyte for a magnesium secondary battery containing

[0009]

Chemical formula

[0010] In formula (1), R1, R2, R3, and R4 are each independently (i) an alkyl group or (ii) an alkyl group having a functional group.

Advantages of the Invention

[0011] According to the present disclosure, a novel non-aqueous electrolyte for a magnesium secondary battery can be provided. Further, according to the present disclosure, a magnesium secondary battery using the non-aqueous electrolyte can be provided.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0013] (Findings on which the present disclosure is based) Magnesium secondary batteries are expected to be high-capacity secondary batteries because they can utilize the two-electron reaction of magnesium. However, since the interaction between divalent magnesium ions and the surrounding solvent is strong, it is difficult for the solvent to desorb from the magnesium ions. That is, in non-aqueous electrolytes for magnesium secondary batteries, the precipitation and dissolution of magnesium metal are unlikely to occur. This is a problem specific to non-aqueous electrolytes for magnesium secondary batteries. For example, in conventional magnesium secondary batteries, a non-aqueous electrolyte obtained by dissolving a magnesium salt in a glyme such as 1,2-dimethoxyethane is used. However, the Coulombic efficiency of magnesium secondary batteries using this non-aqueous electrolyte is low. Due to such problems, in magnesium secondary batteries, there are strong restrictions on the combination of non-aqueous solvents and magnesium salts.

[0014] Based on the above findings, the present inventors have found the following novel non-aqueous electrolyte.

[0015] (Summary of an aspect according to the present disclosure) The non-aqueous electrolyte for a magnesium secondary battery according to the first aspect of the present disclosure is a non-aqueous solvent, a magnesium salt, an organoaluminum art complex salt represented by the following formula (1), and includes.

[0016] [Chemical formula]

[0017] In formula (1), R1, R2, R3, and R4 are each independently (i) an alkyl group or (ii) an alkyl group having a functional group.

[0018] According to the first aspect, the organoaluminum art complex salt can uniformly distribute magnesium ions on the surface of the electrode. As a result, the precipitation and dissolution of metallic magnesium are promoted, and the charge and discharge efficiency of the magnesium secondary battery can be improved.

[0019] In a second aspect of the present disclosure, for example, in the non-aqueous electrolyte for a magnesium secondary battery according to the first aspect, the non-aqueous solvent may contain ether. The magnesium salt can be sufficiently dissolved in ether.

[0020] In a third aspect of the present disclosure, for example, in the non-aqueous electrolyte for a magnesium secondary battery according to the second aspect, the non-aqueous solvent containing ether may contain glyme.

[0021] In a fourth aspect of the present disclosure, for example, in the non-aqueous electrolyte for a magnesium secondary battery according to the third aspect, the glyme may contain at least one selected from the group consisting of 1,2-dimethoxyethane, diglyme, triglyme, and tetraglyme.

[0022] According to the third and fourth aspects, the magnesium salt can be sufficiently dissolved.

[0023] In a fifth aspect of the present disclosure, for example, in the non-aqueous electrolyte for a magnesium secondary battery according to any one of the first to fourth aspects, in the formula (1), R1, R2, R3, and R4 may each independently be -C x H y F z and may satisfy 1 ≤ x ≤ 4, 0 ≤ y < 9, and 1 ≤ z ≤ 9. In the fifth aspect of the present disclosure, the withstand voltage of the complex ion of the organoaluminum art complex salt can be increased. Therefore, the electrochemical stability of the non-aqueous electrolyte can be improved.

[0024] In a sixth aspect of the present disclosure, for example, in the magnesium secondary battery according to any one of the first to fifth aspects, the magnesium salt has, as an anion, Cl - , BF4 - , [N(FSO2)2] - , [N(CF3SO2)2] - , [N(C2F5SO2)2] - , [N(FSO2)(CF3SO2)] - , [C k B m Hn - and at least one selected from the group consisting of [BOR5OR6OR7OR8] - and may contain, k and m may each independently be an integer of 1 or more, k + m = n, and may satisfy n ≦ 60, and R5, R6, R7, and R8 may each independently be (i) an alkyl group or (ii) an alkyl group having a functional group.

[0025] In the seventh aspect of the present disclosure, for example, in the magnesium secondary battery according to any one of the first to fifth aspects, the magnesium salt has, as an anion, [C k B m H n X p - and may contain, k, m, and p may each independently be an integer of 1 or more, k + m ≦ n + p, and may satisfy n + p ≦ 60, and X may be at least one selected from the group consisting of F, Cl, Br, and I.

[0026] According to the sixth and seventh aspects, these anions can form a salt with magnesium.

[0027] The magnesium secondary battery according to the eighth aspect of the present disclosure a positive electrode, a negative electrode, a non-aqueous electrolyte for a magnesium secondary battery according to any one of the first to seventh aspects, and is provided with.

[0028] According to the eighth aspect, by using the non-aqueous electrolyte for a magnesium secondary battery according to any one of the first to seventh aspects, precipitation and dissolution of metallic magnesium can be promoted. As a result, the charge and discharge efficiency of the magnesium secondary battery can be improved.

[0029] ​​Hereinafter, the non-aqueous electrolyte for a magnesium secondary battery according to the embodiment will be described in detail with reference to the drawings. Further, the magnesium secondary battery using the non-aqueous electrolyte will also be described in detail with reference to the drawings.

[0030] The following descriptions all show inclusive or specific examples. The numerical values, compositions, shapes, film thicknesses, electrical characteristics, and the structure of the secondary battery shown below are merely examples and are not intended to limit the present disclosure. In addition, the components not described in the independent claims indicating the most general concept are arbitrary components.

[0031] [1. Non-aqueous electrolyte] The non-aqueous electrolyte for a magnesium secondary battery according to one aspect of the present disclosure contains a non-aqueous solvent, a magnesium salt, and an organoaluminum art complex salt. The organoaluminum art complex salt has a structure represented by the following formula (1). In the following formula (1), R1, R2, R3, and R4 are each independently (i) an alkyl group or (ii) an alkyl group having a functional group. The magnesium salt and the organoaluminum art complex salt are dissolved in the non-aqueous solvent. The organoaluminum art complex salt can uniformly distribute magnesium ions on the surface of the electrode. As a result, the precipitation and dissolution of metallic magnesium are promoted, and the charge-discharge efficiency of the magnesium secondary battery can be improved.

[0032] [Chemical formula]

[0033] The organoaluminum art complex salt can uniformly distribute magnesium ions in the vicinity of the electrode. Therefore, a non-aqueous electrolyte containing the organoaluminum art complex salt can promote the dissolution of metallic magnesium. Accordingly, the Coulombic efficiency of metallic magnesium can be improved according to desired conditions. The "desired conditions" may be, for example, at least one of (i) high magnesium ion conductivity, (ii) being electrochemically stable, (iii) being chemically stable, (iv) being thermally stable, (v) being safe, (vi) having a low environmental impact, and (vii) being inexpensive. For example, by dissolving a magnesium salt at a high concentration in a non-aqueous solvent, the magnesium ion conductivity of the non-aqueous electrolyte can be increased. For example, by selecting a non-aqueous solvent with high oxidation resistance, a non-aqueous electrolyte that is electrochemically stable can be obtained. For example, by selecting a non-aqueous solvent with low toxicity, a non-aqueous electrolyte with high safety can be obtained.

[0034] The "organoaluminum art complex salt" in the present disclosure means a salt having a complex ion of a magnesium ion and an organoaluminum art complex. In the complex ion of the organoaluminum art complex, four oxygen atoms are bonded to an aluminum atom. A substituent is bonded to each of the oxygen atoms.

[0035] The complex ion of the organoaluminum art complex is larger than the complex ion of the organoboron art complex. Therefore, the center-to-center distance between the magnesium ion and the complex ion of the organoaluminum art complex is larger than the center-to-center distance between the magnesium ion and the complex ion of the organoboron art complex. Thereby, the binding force between the magnesium ion and the complex ion of the organoaluminum art complex is weaker than the binding force between the magnesium ion and the complex ion of the organoboron art complex. As a result, the organoaluminum art complex salt can be more easily ionized than the organoboron art complex salt.

[0036] The organoaluminum art complex salt has R1, R2, R3, and R4 as substituents. R1, R2, R3, and R4 may be the same substituents or different substituents. Each of R1, R2, R3, and R4 may independently be an alkyl group. The alkyl group may be linear or branched. The number of carbon atoms of the alkyl group is not particularly limited. By appropriately adjusting the number of carbon atoms of the alkyl group, the organoaluminum art complex salt can be easily dissolved in a non-aqueous solvent. From the viewpoint of solubility in a polar solvent, the number of carbon atoms of the alkyl group may be 1 or more and 4 or less. R1, R2, R3, and R4 may be the same alkyl group or different alkyl groups.

[0037] Each of R1, R2, R3, and R4 may independently be an alkyl group having a functional group. The alkyl group having a functional group means an alkyl group in which at least one of the hydrogen atoms contained in the alkyl group is substituted with a functional group. All of the hydrogen atoms contained in the alkyl group may be substituted with functional groups. When the alkyl group has a plurality of functional groups, the plurality of functional groups may be the same functional group or different functional groups. Examples of the functional group include a halogen group, an amino group, a hydroxyl group, and a carboxyl group.

[0038] The alkyl group having a functional group may be a fluorinated alkyl group. Each of R1, R2, R3, and R4 may independently be a fluorinated alkyl group. The fluorinated alkyl group means an alkyl group in which at least one of the hydrogen atoms contained in the alkyl group is substituted with fluorine. All of the hydrogen atoms contained in the alkyl group may be substituted with fluorine. By using the fluorinated alkyl group, the breakdown voltage resistance of the complex ion of the organoaluminum art complex can be improved. Therefore, the electrochemical stability of the non-aqueous electrolyte can be improved. Furthermore, the higher the number of fluorines contained in the alkyl group, the more the electrochemical stability of the organoaluminum art complex salt can be improved by the inductive effect.

[0039] The alkyl fluoride group may be linear or branched. From the perspective of solubility in polar solvents, the number of carbon atoms in the alkyl fluoride group may be 1 or more and 4 or less. The alkyl fluoride group is represented by, for example, -C x H y F z where 1 ≤ x ≤ 4 is satisfied, 0 ≤ y < 9 is satisfied, and 1 ≤ z ≤ 9 is satisfied. Examples of the alkyl fluoride group include substituents in which at least one hydrogen atom of a hydrogen atom contained in a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, an iso-butyl group, a sec-butyl group, and a tert-butyl group is substituted with a fluorine atom.

[0040] The magnesium salt has an anion. The anion is, for example, a monovalent anion.

[0041] The magnesium salt is Cl - 、BF4 - 、[N(FSO2)2] - 、[N(CF3SO2)2] - 、[N(C2F5SO2)2] - 、[N(FSO2)(CF3SO2)] - 、[C k B m H n - 、and [BOR5OR6OR7OR8] - and contains at least one anion selected from the group consisting of. k and m are each independently an integer of 1 or more. k + m = n, and n ≤ 60 is satisfied. These anions can form a salt with magnesium.

[0042] [BOR5OR6OR7OR8] - ​The magnesium salt containing [it] is an organic boron art complex salt. "Organic boron art complex salt" means a salt having a magnesium ion and a complex ion of an organic boron art complex. In the complex ion of the organic boron art complex, four oxygen atoms are bonded to the boron atom. A substituent is bonded to each of the oxygen atoms. The organic boron art complex salt has R5, R6, R7, and R8 as substituents. R5, R6, R7, and R8 are each independently (i) an alkyl group or (ii) an alkyl group having a functional group. R5, R6, R7, and R8 may be the same substituent or different substituents. Such an organic boron art complex salt can uniformly distribute magnesium ions on the surface of the electrode. As a result, the precipitation and dissolution of metallic magnesium derived from the magnesium salt are promoted, and the electrochemical stability of the non-aqueous electrolyte can be improved.

[0043] R5, R6, R7, and R8 may each independently be an alkyl group. The alkyl group may be linear or branched. The number of carbon atoms of the alkyl group is not particularly limited. By appropriately adjusting the number of carbon atoms of the alkyl group, the organic boron art complex salt can be easily dissolved in a non-aqueous solvent. From the viewpoint of solubility in a polar solvent, the number of carbon atoms of the alkyl group may be 1 or more and 4 or less. R5, R6, R7, and R8 may be the same alkyl group or different alkyl groups.

[0044] R5, R6, R7, and R8 may each independently be an alkyl group having a functional group. An alkyl group having a functional group means an alkyl group in which at least one hydrogen atom contained in the alkyl group is substituted with a functional group. All hydrogen atoms contained in the alkyl group may be substituted with functional groups. When the alkyl group has a plurality of functional groups, the plurality of functional groups may be the same functional group or different functional groups. Examples of the functional group include a halogen group, an amino group, a hydroxyl group, and a carboxyl group.

[0045] The alkyl group having a functional group may be a fluorinated alkyl group. R5, R6, R7, and R8 may each independently be a fluorinated alkyl group. All hydrogen atoms contained in the alkyl group may be substituted with fluorine. By using a fluorinated alkyl group, the withstand voltage of the complex ion of the organoboron art complex can be improved. Therefore, the electrochemical stability of the non-aqueous electrolyte can be improved. Furthermore, the greater the number of fluorine atoms contained in the alkyl group, the more the electrochemical stability of the organoboron art complex salt can be improved by the inductive effect.

[0046] The fluorinated alkyl group may be linear or branched. From the viewpoint of solubility in a polar solvent, the number of carbon atoms of the fluorinated alkyl group may be 1 or more and 4 or less. The fluorinated alkyl group is represented by, for example, -C x H y F z where 1 ≤ x ≤ 4 is satisfied, 0 ≤ y < 9 is satisfied, and 1 ≤ z ≤ 9 is satisfied. Examples of the fluorinated alkyl group include substituents in which at least one hydrogen atom contained in a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, an iso-butyl group, a sec-butyl group, and a tert-butyl group is substituted with fluorine.

[0047] The magnesium salt may be a magnesium imide salt. That is, the magnesium imide salt may contain at least one anion selected from the group consisting of [N(FSO2)2] - , [N(CF3SO2)2] - , [N(C2F5SO2)2] - , and [N(FSO2)(CF3SO2)] - and these anions can form a salt with magnesium.

[0048] The magnesium salt is [C k B m H n X p - ​It may contain. k, m, and p are each independently an integer of 1 or more. k + m ≤ n + p and n + p ≤ 60 are satisfied. X is at least one selected from the group consisting of F, Cl, Br, and I. [C satisfying the above conditions k B m H n X p can form a salt with magnesium.

[0049] The non-aqueous solvent is not particularly limited as long as it can dissolve the magnesium salt. The non-aqueous solvent may contain ether. The magnesium salt can be sufficiently dissolved in ether. From the viewpoint of solubility, the non-aqueous solvent may contain glyme. Glyme can form a bidentate coordination with magnesium ions. By using glyme, the solubility of the magnesium imide salt in the non-aqueous solvent can be improved. Examples of glyme include 1,2-dimethoxyethane (DME), diglyme, triglyme, and tetraglyme. From the viewpoint of oxidation resistance, the non-aqueous solvent may contain fluorinated ether. Fluorinated ether means an ether in which at least one of the hydrogen atoms contained in the ether is replaced by fluorine.

[0050] The organoaluminum art complex salt may form a coordination bond with an ether contained in a non-aqueous solvent or an ether different from the ether. Specifically, the magnesium ion of the organoaluminum art complex salt may form a coordination bond with an ether. Due to the coordination bond formed between the organoaluminum art complex salt and the ether, when the organoaluminum art complex salt is dissolved in a non-aqueous solvent, the dissociation of magnesium ions is promoted. The ether that forms a coordination bond with the organoaluminum art complex salt may contain glyme. By using glyme, the number of ethers that form a coordination bond with the magnesium ion of the organoaluminum art complex salt can be reduced. As a result, the breakdown voltage resistance of the non-aqueous electrolyte can be improved, and the solubility of the organoaluminum art complex salt in the non-aqueous solvent can be improved. When the organoaluminum art complex salt is dissolved in a non-aqueous solvent, the ether coordinated to the organoaluminum art complex salt and the ether contained in the non-aqueous solvent may be substituted.

[0051] The ether that coordinates to the magnesium ion of the organoaluminum art complex salt may contain tetrahydrofuran (hereinafter referred to as "THF"). The binding force of THF to the magnesium ion is weaker than the binding force of glyme to the magnesium ion. Therefore, after the organoaluminum art complex salt is dissolved in a non-aqueous solvent, THF coordinated to the magnesium ion can be easily substituted by the non-aqueous solvent. That is, the solubility of the organoaluminum art complex salt in the non-aqueous solvent can be further improved.

[0052] The concentration of the magnesium salt in the non-aqueous electrolyte is not particularly limited. By appropriately setting the concentration of the magnesium salt, the conductivity of magnesium ions can be improved. The concentration of the magnesium salt in the non-aqueous electrolyte may be higher than the concentration of the organoaluminum art complex salt in the non-aqueous electrolyte. When the concentration of the magnesium salt is higher than the concentration of the organoaluminum art complex salt, the thermal stability of the non-aqueous electrolyte can be improved.

[0053] [2. Magnesium Secondary Battery] [2-1. Overall Configuration] The non-aqueous electrolyte according to this embodiment can be used in a magnesium secondary battery. The magnesium secondary battery includes a positive electrode, a negative electrode, and a non-aqueous electrolyte having magnesium ion conductivity. As the non-aqueous electrolyte, the non-aqueous electrolyte described in the above item [1. Non-aqueous electrolyte] can be appropriately used. By using the non-aqueous electrolyte of the present disclosure, the precipitation and dissolution of metallic magnesium can be promoted. As a result, the charge-discharge efficiency of the magnesium secondary battery can be improved.

[0054] FIG. 1 is a cross-sectional view schematically showing a configuration example of a magnesium secondary battery 10.

[0055] The magnesium secondary battery 10 includes a positive electrode 21, a negative electrode 22, a separator 14, a case 11, a sealing plate 15, and a gasket 18. The separator 14 is disposed between the positive electrode 21 and the negative electrode 22. The positive electrode 21, the negative electrode 22, and the separator 14 are impregnated with a non-aqueous electrolyte, and these are housed in the case 11. The case 11 is closed by the gasket 18 and the sealing plate 15.

[0056] The structure of the magnesium secondary battery 10 may be cylindrical, rectangular, button-shaped, coin-shaped, or flat.

[0057] [2-2. Positive Electrode] The positive electrode 21 includes a positive electrode current collector 12 and a positive electrode active material layer 13 disposed on the positive electrode current collector 12. The positive electrode active material layer 13 is disposed between the positive electrode current collector 12 and the separator 14.

[0058] The positive electrode active material layer 13 contains a positive electrode active material. The positive electrode active material may be graphite fluoride, a metal oxide, or a metal halide. The metal oxide and the metal halide may contain at least one selected from the group consisting of scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, and zinc and magnesium. The positive electrode active material may be a sulfide such as Mo6S8, Mo9Se11 It may also be a chalcogenide compound such as the following.

[0059] As the positive electrode active material, MgM2O4, MgRO2, MgXSiO4, and Mg x Z y AO z F w are mentioned. Here, M contains at least one selected from the group consisting of Mn, Co, Cr, Ni, and Fe. R contains at least one selected from the group consisting of Mn, Co, Cr, Ni, and Al. X contains at least one selected from the group consisting of Mn, Co, Ni, and Fe. Z contains at least one selected from the group consisting of transition metals, Sn, Sb, and In. A contains at least one selected from the group consisting of P, Si, and S. 0 < x ≦ 2 is satisfied. 0.5 ≦ y ≦ 1.5 is satisfied. z is 3 or 4. 0.5 ≦ w ≦ 1.5 is satisfied.

[0060] The positive electrode active material layer 13 may further contain at least one selected from the group consisting of a conductive material and a binder, if necessary.

[0061] Examples of the conductive material include carbon materials, metals, inorganic compounds, and conductive polymers. Examples of the carbon materials include graphite, acetylene black, carbon black, ketjen black, carbon whiskers, needle coke, and carbon fibers. Examples of the graphite include natural graphite and artificial graphite. Examples of the natural graphite include massive graphite and flaky graphite. Examples of the metals include copper, nickel, aluminum, silver, and gold. Examples of the inorganic compounds include tungsten carbide, titanium carbide, tantalum carbide, molybdenum carbide, titanium boride, and titanium nitride. One of these materials may be used alone, or a mixture of two or more of these materials may be used.

[0062] Examples of the binder include fluororesin, thermoplastic resin, ethylene propylene diene monomer (EPDM) rubber, sulfonated EPDM rubber, and natural butyl rubber (NBR). Examples of the fluororesin include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), and fluororubber. Examples of the thermoplastic resin include polypropylene and polyethylene. These materials may be used alone or as a mixture of two or more of these materials.

[0063] Examples of the solvent for dispersing the positive electrode active material, the conductive material, and the binder include N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethylenetriamine, N,N-dimethylaminopropylamine, ethylene oxide, and tetrahydrofuran. A thickener may be added to the dispersant. Examples of the thickener include carboxymethyl cellulose and methyl cellulose.

[0064] The positive electrode active material layer 13 is formed, for example, by the following method. First, these materials are mixed so as to obtain a mixture of the positive electrode active material, the conductive material, and the binder. Next, an appropriate solvent is added to this mixture to obtain a paste-like positive electrode mixture. Next, this positive electrode mixture is applied to the surface of the positive electrode current collector 12 and dried. Thereby, the positive electrode active material layer 13 is formed on the positive electrode current collector 12. The positive electrode active material layer 13 may be compressed in order to increase the electrode density.

[0065] The film thickness of the positive electrode active material layer 13 is not particularly limited and is, for example, 1 μm or more and 100 μm or less.

[0066] The material of the positive electrode current collector 12 is, for example, a single metal or an alloy. More specifically, the material of the positive electrode current collector 12 may be at least one metal selected from the group consisting of copper, chromium, nickel, titanium, platinum, gold, aluminum, tungsten, iron, and molybdenum or an alloy thereof. The material of the positive electrode current collector 12 may be stainless steel.

[0067] The positive electrode current collector 12 may be plate-shaped or foil-shaped. The positive electrode current collector 12 may be a laminated film.

[0068] When the case 11 also serves as the positive electrode current collector, the positive electrode current collector 12 may be omitted.

[0069] [2-3. Negative electrode] The negative electrode 22 includes, for example, a negative electrode active material layer 17 containing a negative electrode active material and a negative electrode current collector 16. The negative electrode active material layer 17 is disposed between the negative electrode current collector 16 and the separator 14.

[0070] The negative electrode active material layer 17 contains a negative electrode active material capable of inserting and extracting magnesium ions. Examples of the negative electrode active material include carbon materials. Examples of the carbon materials include graphite, non-graphite carbon, and graphite intercalation compounds. Examples of the non-graphite carbon include hard carbon and coke.

[0071] The negative electrode active material layer 17 may further contain at least one selected from the group consisting of a conductive material and a binder, if necessary. As the conductive material, binder, solvent, and thickener, for example, the conductive material, binder, solvent, and thickener described in item [2-2. Positive electrode] can be appropriately used.

[0072] The film thickness of the negative electrode active material layer 17 is not particularly limited, and is, for example, 1 μm or more and 50 μm or less.

[0073] Alternatively, the negative electrode active material layer 17 contains a negative electrode active material capable of depositing and dissolving magnesium. In this case, examples of the negative electrode active material include Mg metal and Mg alloys. The Mg alloy is, for example, an alloy of magnesium and at least one selected from the group consisting of aluminum, silicon, gallium, zinc, tin, manganese, bismuth, and antimony.

[0074] As the material of the negative electrode current collector 16, for example, the same materials as those of the positive electrode current collector 12 described in item [2-2. Positive electrode] can be appropriately used. The negative electrode current collector 16 may be plate-shaped or foil-shaped.

[0075] When the sealing plate 15 also serves as the negative electrode current collector, the negative electrode current collector 16 may be omitted.

[0076] When the negative electrode current collector 16 is made of a material capable of depositing and dissolving magnesium on its surface, the negative electrode active material layer 17 may be omitted. That is, the negative electrode 22 may be composed only of the negative electrode current collector 16 capable of depositing and dissolving magnesium. In this case, the negative electrode current collector 16 may be stainless steel, nickel, copper, or iron.

[0077] [2-4. Separator] Examples of the material of the separator 14 include microporous films, woven fabrics, and non-woven fabrics. The material of the separator 14 may be a polyolefin such as polypropylene or polyethylene. The thickness of the separator 14 is, for example, 10 μm or more and 300 μm or less. The separator 14 may be a single-layer film composed of one kind of material, or a composite film or a multilayer film composed of two or more kinds of materials. The porosity of the separator 14 is, for example, 30% or more and 70% or less.

[0078] (Example) [3. Experimental Results] [3-1. Preparation of Non-aqueous Electrolyte] [Sample 1] As the non-aqueous solvent, triglyme (G3) was used. Mg[N(CF3SO2)2]2 (hereinafter referred to as Mg(TFSI)2), which is a magnesium salt, was dissolved in triglyme at a concentration of 0.35 mol / L. Further, an organic aluminum art complex salt represented by the chemical formula Mg[Al(O(CF3)3)4]2·7THF, which can form a coordination bond with tetrahydrofuran (THF), was dissolved at a concentration of 0.05 mol / L to prepare the non-aqueous electrolyte of Sample 1.

[0079] [Sample 2] Triglyme was used as the non-aqueous solvent. The non-aqueous electrolyte of Sample 2 was prepared by dissolving Mg(TFSI)2 at a concentration of 0.40 mol / L in triglyme.

[0080] The concentration of magnesium ions contained in each of Sample 1 and Sample 2 was 0.40 mol / L.

[0081] [Sample 3] Triglyme was used as the non-aqueous solvent. Mg(TFSI)2 was dissolved in triglyme at a concentration of 0.85 mol / L. Further, the non-aqueous electrolyte of Sample 3 was prepared by dissolving Mg[Al(O(CF3)3)4]2·7THF at a concentration of 0.15 mol / L.

[0082] [Sample 4] Triglyme was used as the non-aqueous solvent. The non-aqueous electrolyte of Sample 4 was prepared by dissolving Mg(TFSI)2 at a concentration of 1.0 mol / L in triglyme.

[0083] The concentration of magnesium ions contained in each of Sample 3 and Sample 4 was 1.0 mol / L.

[0084] [3-2. Evaluation of CV Characteristics] Cyclic voltammetry (i.e., CV) measurements were performed on the obtained non-aqueous electrolyte. A beaker cell was used as the measurement cell, and a potentiostat / galvanostat (VSP-300 manufactured by BioLogic) was used as the measurement device. A platinum disk electrode was used as the working electrode. A 5 mm×40 mm magnesium ribbon was used as the reference electrode and the counter electrode. Figures 2 and 3 show the results of the cyclic voltammetry measurements.

[0085] The amount of electricity required for the precipitation of metallic magnesium and the amount of electricity required for the dissolution of metallic magnesium were calculated from the cyclic voltammogram. The Coulomb efficiency was calculated by dividing the amount of electricity required for the dissolution of metallic magnesium by the amount of electricity required for the precipitation of metallic magnesium.

[0086] Figure 2 is a graph showing the cyclic voltammograms of Sample 1 and Sample 2. The vertical axis represents the current flowing through the working electrode, and the horizontal axis represents the potential of the working electrode with respect to the reference electrode. Figure 2 shows the results in the sweeping range from -1 V to 3 V. The sweeping rate of the potential was 25 mV / s. As shown in Figure 2, a current was observed in Sample 1. The current was considered to flow due to the precipitation and dissolution of metallic magnesium. The Coulomb efficiency of Sample 1 was 19%. On the other hand, the Coulomb efficiency of Sample 2 was 10%. Compared with the Coulomb efficiency of Sample 2, the Coulomb efficiency of Sample 1 was significantly improved. The non-aqueous electrolyte of Sample 1 contained an organoaluminum art complex salt, and it was considered that the organoaluminum art complex salt promoted the precipitation and dissolution of metallic magnesium.

[0087] From the above results, it is considered that the non-aqueous electrolyte of Sample 1 is suitable for a magnesium secondary battery.

[0088] Figure 3 is a graph showing the cyclic voltammograms of Sample 3 and Sample 4. The vertical axis represents the current flowing through the working electrode, and the horizontal axis represents the potential of the working electrode with respect to the reference electrode. Figure 3 shows the results in the sweeping range from -1 V to 3 V. The sweeping rate of the potential was 25 mV / s. As shown in Figure 3, a current was observed in Sample 3. The current was considered to flow due to the precipitation and dissolution of metallic magnesium. The Coulomb efficiency of Sample 3 was 46%. On the other hand, the Coulomb efficiency of Sample 4 was 9%. Compared with the Coulomb efficiency of Sample 4, the Coulomb efficiency of Sample 3 was significantly improved. The non-aqueous electrolyte of Sample 3 contained an organoaluminum art complex salt, and it was considered that the organoaluminum art complex salt promoted the precipitation and dissolution of metallic magnesium.

[0089] From the results of Sample 1 and Sample 3, it is considered that by increasing the concentration of magnesium ions contained in the non-aqueous electrolyte, the organoaluminum art complex salt further promotes the precipitation and dissolution of metallic magnesium.

[0090] From the above results, it is considered that the non-aqueous electrolyte of Sample 3 is suitable for a magnesium secondary battery.

Industrial Applicability

[0091] The non-aqueous electrolyte of the present disclosure can be used in a magnesium secondary battery.

Explanation of Signs

[0092] 10 Magnesium secondary battery 11 Case 12 Positive current collector 13 Positive electrode active material layer 14 Separator 15 Sealing plate 16 Negative current collector 17 Negative electrode active material layer 18 Gasket 21 Positive electrode 22 Negative electrode

Claims

1. A non-aqueous solvent, a magnesium salt, an organoaluminum art complex salt represented by the following formula (1), and a non-aqueous electrolyte for a magnesium secondary battery containing the same. 【Chemical 1】 [In formula (1), R 1 , R 2 , R 3 , and R 4 are each independently an alkyl group having a functional group (however, excluding those having an ether bond as the functional group).]

2. The non-aqueous solvent contains ether, and the non-aqueous electrolyte for a magnesium secondary battery according to Claim 1.

3. The non-aqueous solvent containing ether contains glyme, and the non-aqueous electrolyte for a magnesium secondary battery according to Claim 2.

4. The glyme contains at least one selected from the group consisting of 1,2-dimethoxyethane, diglyme, triglyme, and tetraglyme, and the non-aqueous electrolyte for a magnesium secondary battery according to Claim 3.

5. In the formula (1), R 1 , R 2 , R 3 , and R 4 are each independently represented by -C x H y F z and Satisfying 1 ≦ x ≦ 4, 0 ≦ y < 9, and 1 ≦ z ≦ 9, and the non-aqueous electrolyte for a magnesium secondary battery according to any one of Claims 1 to 4.

6. The magnesium salt contains, as an anion, Cl - , BF 4 - , [N(FSO 2 )( 2 ) - , [N(CF 3 SO 2 )( 2 ) - , [N(C 2 F 5 SO 2 )( 2 ) - , [N(FSO 2 )(CF 3 SO 2 )] - , [C k B m H n ) - , and [BOR 5 OR 6 OR 7 OR 8 )] - and contains at least one selected from the group consisting of k and m are each independently an integer of 1 or more, satisfying k + m = n and n ≦ 60, and R 5 , R 6 , R 7 , and R 8 is, independently of one another, (i) an alkyl group or (ii) an alkyl group having a functional group and the non-aqueous electrolyte for a magnesium secondary battery according to any one of Claims 1 to 5.

7. A non-aqueous solvent, a magnesium salt, an organoaluminum art complex salt represented by the following formula (1), and containing, [Chemical Formula 2] [In formula (1), R1, R2, R3, and R4 are each independently (i) an alkyl group or (ii) an alkyl group having a functional group.] The magnesium salt contains, as an anion, [C k B m H n X p - and k, m, and p are each independently an integer of 1 or more, satisfying k + m ≦ n + p and n + p ≦ 60, and X is at least one selected from the group consisting of F, Cl, Br, and I, and the non-aqueous electrolyte for a magnesium secondary battery.

8. A non-aqueous solvent, a magnesium salt, an organoaluminum art complex salt represented by the following formula (1), and a non-aqueous electrolyte for a magnesium secondary battery containing the same, 【Chemical Formula 3】 [In formula (1), R1, R2, R3, and R4 are each independently (i) an alkyl group or (ii) an alkyl group having a functional group.] In the non-aqueous electrolyte for a magnesium secondary battery, the concentration of the magnesium salt is higher than the concentration of the organoaluminum art complex salt, and the non-aqueous electrolyte for a magnesium secondary battery.

9. The functional groups in R1, R2, R3, and R4 are each independently a halogen group, an amino group, a hydroxyl group, or a carboxyl group, and the non-aqueous electrolyte for a magnesium secondary battery according to any one of Claims 1 to 8.

10. The functional groups in R1, R2, R3, and R4 are halogen groups. The non-aqueous electrolyte for a magnesium secondary battery according to any one of Claims 1 to 8.

11. a positive electrode, a negative electrode, a non-aqueous electrolyte for a magnesium secondary battery according to any one of Claims 1 to 10, A magnesium secondary battery comprising:

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