JP2014232719A - Magnesium ion secondary battery, battery pack using the same, and electrolytic solution for magnesium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnesium ion secondary battery which is superior in heat resistance and charge and discharge characteristics.SOLUTION: A magnesium ion secondary battery 1 comprises: a positive electrode 21; a negative electrode 22; and an electrolytic solution 3. The electrolytic solution 3 contains a mixture of a dialkyl glycol ether expressed by the general formula (1) and a Mg compound formed by a Mg atom with two ligands identical to each other combined thereto. The ligands have a hydrophobic structure at a position which is the farthest from the Mg atom. [Rand Rindependently represent an alkyl group having 1-6 carbon atoms with fluorine substituted or unsubstituted for at least part of hydrogen, or a phenyl group or cyclohexyl group with a halogen atom substituted or unsubstituted for part of hydrogen; and n is an integer of 1-12.]

Description

  The present invention relates to a magnesium ion secondary battery, a battery pack using the same, and an electrolyte for a magnesium ion secondary battery.

  In recent years, research and development related to secondary batteries represented by lithium ion secondary batteries and the like have been actively promoted as a clean energy source with a low environmental load. Lithium ion secondary batteries are portable electronic devices, etc. Widely used as a power source. However, metallic lithium is an expensive material limited in terms of resources, and the safety of lithium ion batteries has been regarded as a problem due to the high activity of lithium.

  In contrast, magnesium is abundant in resources and is much cheaper than lithium. In addition, in a secondary battery using magnesium, a high amount of electricity per unit volume and high safety can be expected. Therefore, recently, a magnesium ion secondary battery has been attracting attention, and research and development has been actively conducted.

  In the development of a magnesium ion secondary battery, the selection of the electrolytic solution is extremely important. For example, not only water or a protic organic solvent but also an aprotic organic solvent such as esters and acrylonitrile cannot be used as a solvent constituting the electrolytic solution. This is because when these solvents are used, a passive film that does not allow magnesium ions to pass through is formed on the surface of the magnesium metal. This problem of passivating film formation is one of the obstacles to the practical use of magnesium ion secondary batteries.

  Therefore, a magnesium ion secondary battery using an organic ether such as tetrahydrofuran or ethylene glycol dimethyl ether as a solvent for an electrolytic solution has been proposed (see Patent Document 1).

JP 2012-182124 A

  The magnesium ion secondary battery described above is expected to be used as a power source for electronic devices such as mobile phones and laptop computers and electric vehicles. The secondary battery is exposed to a higher temperature atmosphere. Therefore, development of a magnesium ion secondary battery with more excellent heat resistance is desired.

  Tetrahydrofuran as a solvent for an electrolyte solution disclosed in Patent Document 1 has a low boiling point (boiling point: 66 ° C.). Therefore, when a magnesium ion secondary battery is exposed to a high temperature atmosphere, the electrolyte solution is decomposed. There is a problem that gasification is caused, cycle characteristics are deteriorated, battery internal pressure is increased, and the battery is expanded. In addition, an electrolytic solution using tetrahydrofuran as a solvent has extremely low stability in a dry environment and is difficult to handle. Therefore, the magnesium ion secondary battery using tetrahydrofuran as the solvent for the electrolyte also has a problem that industrial production in a production line in a dry environment is extremely difficult. Therefore, a new proposal of an electrolytic solution for a magnesium ion secondary battery excellent in heat resistance and handleability is eagerly desired for practical use.

  In addition, with increasing performance and miniaturization of electronic devices and the like, there is an increasing demand for development of a laminate-type thin secondary battery that can achieve space saving and large capacity. A laminate-type thin secondary battery is generally manufactured by enclosing a power generation element formed by laminating a positive electrode, a separator, and a negative electrode, and an electrolytic solution in a laminate outer package. At this time, if bubbles remain in the laminate outer package (magnesium ion secondary battery), the battery characteristics may be deteriorated, so the laminate package is vacuum-sealed.

  There is a problem that an electrolytic solution using tetrahydrofuran having a low boiling point as a solvent tends to volatilize when vacuum-sealed in a laminate outer package. In other words, when tetrahydrofuran is used as the solvent for the electrolytic solution, there is a problem that a laminate-type thin secondary battery cannot be manufactured.

  On the other hand, ethylene glycol dimethyl ether as a solvent for an electrolytic solution disclosed in Patent Document 1 has a higher boiling point compared to tetrahydrofuran (boiling point: 85.2 ° C.), and therefore, an electrolytic solution for a conventional magnesium ion secondary battery. Compared to tetrahydrofuran used as a solvent for the electrolyte, the electrolyte solution is less likely to evaporate when vacuum-sealed in the laminate outer package. However, charge / discharge characteristics in a magnesium ion secondary battery using an electrolytic solution containing ethylene glycol dimethyl ether as a solvent have not yet been confirmed.

  In view of the above problems, the present invention uses an electrolytic solution containing a high-boiling solvent, and has excellent heat resistance and handleability, and has excellent charge / discharge characteristics, and a magnesium ion secondary battery electrolysis for the magnesium ion secondary battery. An object is to provide a liquid and a magnesium ion secondary battery pack.

  In order to solve the above-described problems, the present invention provides a magnesium ion secondary battery having a positive electrode, a negative electrode, and an electrolyte solution, wherein the electrolyte solution is a dialkyl glycol ether represented by the following general formula (1). And a mixture of a magnesium compound in which two identical ligands are bonded to a magnesium atom, and the ligand has a hydrophobic structure at a position farthest from the magnesium atom. An ion secondary battery is provided (Invention 1).

式中、Ｒ₁及びＲ₂は、それぞれ独立して炭素数１〜６のアルキル基及び少なくとも一部の水素がフッ素置換されたアルキル基、フェニル基及び少なくとも一部の水素がハロゲン原子で置換されたフェニル基、並びにシクロヘキシル基及び少なくとも一部の水素がハロゲン原子で置換されたシクロヘキシル基のうちのいずれかであり、ｎは１〜１２の整数である。

In the formula, R ₁ and R ₂ are each independently an alkyl group having 1 to 6 carbon atoms, an alkyl group in which at least a part of hydrogen is substituted with fluorine, a phenyl group, and at least a part of hydrogen is substituted with a halogen atom. And a phenyl group, a cyclohexyl group, and a cyclohexyl group in which at least a part of hydrogen is substituted with a halogen atom, and n is an integer of 1 to 12.

  According to the invention (Invention 1), the heat resistance of the magnesium ion secondary battery can be improved by using the dialkyl glycol ether having a higher boiling point than conventional tetrahydrofuran as the solvent of the electrolytic solution, By using a magnesium compound in which two identical ligands are bonded to a magnesium atom as a solute of the electrolytic solution, and the ligand has a hydrophobic structure at a position farthest from the magnesium atom, Excellent charge / discharge characteristics can be exhibited in combination with the dialkyl glycol ether.

  In the said invention (invention 1), the said ligand has either the C1-C6 alkyl group and the said alkyl group by which at least one part hydrogen was fluorine-substituted in the position furthest from the said magnesium atom. (Invention 2).

  In the above inventions (Inventions 1 and 2), the magnesium compound is preferably formed by bonding two disilazane groups to the magnesium atom (Invention 3), and the magnesium compound is magnesium bis (hexamethyldisilazide). (Invention 4)

  Moreover, in the said invention (invention 1 and 2), it is preferable that the said magnesium compound is diisopropyl magnesium or dibutyl magnesium (invention 5).

  In the above inventions (Inventions 1 to 5), the dialkyl glycol ether may be ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, pentaethylene glycol dimethyl ether, hexaethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, or triethylene glycol. It is preferably butyl methyl ether (Invention 6), more preferably triethylene glycol dialkyl ether or tetraethylene glycol dialkyl ether (Invention 7), triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether or triethylene glycol butyl methyl. Ete In particular, particularly preferably triethylene glycol dimethyl ether or tetraethylene glycol dimethyl ether (invention 8).

  In the said invention (invention 1-8), it is preferable that the said positive electrode, the said negative electrode, and the said electrolyte solution are sealed in the laminate exterior body (invention 9).

  In addition, the present invention includes a mixture of a dialkyl glycol ether represented by the following general formula (1) and a magnesium compound in which two identical ligands are bonded to a magnesium atom, Provided is an electrolyte solution for a magnesium ion secondary battery, which has a hydrophobic structure at a position farthest from the magnesium atom (Invention 10).

式中、Ｒ₁及びＲ₂は、それぞれ独立して炭素数１〜６のアルキル基及び少なくとも一部の水素がフッ素置換されたアルキル基、フェニル基及び少なくとも一部の水素がハロゲン原子で置換されたフェニル基、並びにシクロヘキシル基及び少なくとも一部の水素がハロゲン原子で置換されたシクロヘキシル基のうちのいずれかであり、ｎは１〜１２の整数である。

In the formula, R ₁ and R ₂ are each independently an alkyl group having 1 to 6 carbon atoms, an alkyl group in which at least a part of hydrogen is substituted with fluorine, a phenyl group, and at least a part of hydrogen is substituted with a halogen atom. And a phenyl group, a cyclohexyl group, and a cyclohexyl group in which at least a part of hydrogen is substituted with a halogen atom, and n is an integer of 1 to 12.

  In the said invention (invention 10), the said ligand has either the C1-C6 alkyl group and the said alkyl group by which at least one part hydrogen was fluorine-substituted in the position furthest from the said magnesium atom. (Invention 11)

  In the above inventions (Inventions 10 and 11), the magnesium compound is preferably formed by bonding two disilazane groups to the magnesium atom (Invention 12), and the magnesium compound is magnesium bis (hexamethyldisilazide). (Invention 13)

  Moreover, in the said invention (invention 10 and 11), it is preferable that the said magnesium compound is diisopropyl magnesium or dibutyl magnesium (invention 14).

  In the above inventions (Inventions 10 to 14), the dialkyl glycol ether may be ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, pentaethylene glycol dimethyl ether, hexaethylene glycol dimethyl ether, polyethylene glycol dimethyl ether or triethylene glycol. It is preferably butyl methyl ether (Invention 15), more preferably triethylene glycol dialkyl ether or tetraethylene glycol dialkyl ether (Invention 16), triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether or triethylene glycol butyl methyl. Particularly preferably an ether (invention 17).

  Furthermore, the present invention has a storage case, a magnesium ion secondary battery according to the above inventions (Inventions 1 to 9), and a protection circuit including an overcharge protection function and an overdischarge protection function. Provided is a magnesium ion secondary battery pack characterized by containing a magnesium ion secondary battery and the protection circuit (Invention 18).

  ADVANTAGE OF THE INVENTION According to this invention, while using the electrolyte solution containing a high boiling-point solvent, while being excellent in heat resistance and handleability, the magnesium ion secondary battery which has favorable charging / discharging characteristics, the electrolyte solution for the said magnesium ion secondary battery, and magnesium An ion secondary battery pack can be provided.

FIG. 1 is a partial cross-sectional view showing a schematic configuration of a magnesium ion secondary battery according to an embodiment of the present invention. FIG. 2 is a perspective view showing a schematic configuration of a magnesium ion secondary battery according to an embodiment of the present invention. FIG. 3 is an exploded perspective view showing a schematic configuration of the magnesium ion secondary battery pack according to the embodiment of the present invention.

Embodiments of the present invention will be described with reference to the drawings.
[Magnesium ion secondary battery]
FIG. 1 is a cross-sectional view illustrating a schematic configuration of a magnesium ion secondary battery according to an embodiment of the present invention, and FIG. 2 is a perspective view illustrating a schematic configuration of a magnesium ion secondary battery according to an embodiment of the present invention. FIG.

  As shown in FIGS. 1 and 2, the magnesium ion secondary battery 1 according to the present embodiment includes a laminate 2 in which sheet-like positive electrodes 21 and negative electrodes 22 are alternately stacked with separators 23 interposed therebetween, and electrolysis. A liquid 3, a positive electrode lead wire 24 connected to the positive electrode 21, a negative electrode lead wire (not shown) connected to the negative electrode 22, and a laminate outer body 4 that stores them are provided.

The positive electrode 21 includes a positive electrode current collector such as an aluminum plate, a gold plate, and a platinum plate having a thickness of about 10 to 100 μm, and a positive electrode provided on the positive electrode current collector capable of reversibly inserting and removing magnesium ions. Active material. Examples of the positive electrode active material include graphite fluoride ((CF) _n ); manganese oxide such as manganese dioxide (MnO ₂ ); vanadium oxide such as divanadium pentoxide (V ₂ O ₅ ); sulfur and sulfur compounds ; it can be used Chevrel compounds; magnesium copper oxide _{(Mg x Cu y O z)} ; magnesium iron oxide _{(Mg x Fe y O z)} .

  The negative electrode 22 includes a negative electrode current collector such as a copper plate, a gold plate, and a platinum plate having a thickness of about 10 to 100 μm, and a negative electrode active material (such as various magnesium alloys) provided on the negative electrode current collector and capable of supplying magnesium ions. ). Note that a magnesium alloy plate may be used as the negative electrode 22 and may have both functions of the negative electrode current collector and the negative electrode active material.

  The positive electrode 21 is connected to a positive electrode external terminal 25 by a positive electrode lead wire 24, and the negative electrode 22 is connected to a negative electrode external terminal 26 by a negative electrode lead wire (not shown).

  Each of the positive electrode external terminal 25 and the negative electrode external terminal 26 is constituted by one metal plate, and one end side thereof is sandwiched by the laminate outer package 4 and integrated with the laminate outer package 4, and the other end side is The laminate exterior body 4 protrudes outward.

  A separator 23 is provided between the positive electrode 21 and the negative electrode 22 for insulating them. There is no restriction | limiting in particular as the separator 23, For example, single layer or multilayer porous films, such as polyethylene, a polypropylene, a cellulose, etc. can be used.

  The electrolytic solution 3 includes a mixture of a predetermined magnesium compound as a solute and a predetermined dialkyl glycol ether as a solvent. By using the electrolytic solution 3 containing a mixture of a predetermined dialkyl glycol ether having a relatively high boiling point and a predetermined magnesium compound, a magnesium ion secondary battery having excellent heat resistance can be obtained. Moreover, it can be set as the magnesium ion secondary battery excellent in the charge / discharge characteristic by combining the predetermined magnesium compound as a solute with the predetermined dialkyl glycol ether as a solvent. Furthermore, volatilization of the electrolyte solution 3 can be suppressed in the vacuum sealing step in the manufacturing process of the laminate type magnesium ion secondary battery. Furthermore, since the dialkyl glycol ether as a solvent is excellent in handleability in a dry environment, a magnesium ion secondary battery that can be easily industrially produced in a production line can be obtained.

  In the magnesium compound, two ligands having the same molecular structure are bonded to a magnesium atom, and the ligand has a hydrophobic structure at a position farthest from the magnesium atom. In the present embodiment, the “hydrophobic structure” means a molecular structure that can exhibit hydrophobicity, and a part of the molecular structure of the ligand may be a hydrophobic structure. The entire molecular structure may be a hydrophobic structure.

  Although the specific complex structure contained in the electrolytic solution 3 containing the mixture of the dialkyl glycol ether and the magnesium compound is unknown, complex ions are formed by the dialkyl glycol ether and the magnesium ion derived from the magnesium compound. It is considered a thing.

  In this complex ion formation, it is presumed that magnesium ions are generated by breaking the bond between the two ligands of the magnesium compound. At this time, when the two ligands bonded to the magnesium atom are different (having different molecular structures), the bond of one ligand is cut, but the bond of the other ligand is cut. It is thought that it may remain without being. If one of the ligands is still bonded to the magnesium atom, it is considered difficult to form a stable complex ion (cation) with the dialkyl glycol ether. However, in this embodiment, the two ligands bonded to the magnesium atom have the same molecular structure, so that even if the conditions for cutting the bond between the two ligands are substantially the same, It is thought that the ligand bond is broken together. Therefore, it is considered that complex ions (cations) are stably formed by dialkyl glycol ether and magnesium ions.

  On the other hand, in order for the complex ion (cation) to exist stably, it is necessary that the two ligands cleaved from the magnesium compound serve as counter ions that bind to the complex ion (cation). It is believed that there is. At this time, it is considered that the ligand has a hydrophobic structure, thereby exhibiting an affinity for dialkyl glycol ether (affinity due to hydrophobic interaction). Therefore, it is presumed that a counter ion constituted by a ligand cleaved from a magnesium compound can exist stably with the complex ion (cation). Thereby, in the electrolyte solution 3 which concerns on this embodiment, it is thought that a solvation structure can be stably formed with a dialkyl glycol ether and a magnesium compound.

  As the above-mentioned ligand, those having any one of an alkyl group having 1 to 6 carbon atoms and one in which at least a part of hydrogen of the alkyl group is fluorine-substituted at a position farthest from the magnesium atom are suitable, For example, disilazane groups such as hexamethyldisilazane group; alkyl groups having 1 to 6 carbon atoms such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, pentyl group, hexyl group; trifluoromethanesulfonylimide group Those having a sulfonylimide group such as a trichloromethanesulfonylimide group are preferred.

  As such a magnesium compound, for example, magnesium bis (hexamethyldisilazide), diisopropylmagnesium, dibutylmagnesium, magnesium bis (trifluoromethanesulfonylimide) and the like can be used. In addition, dialkyl magnesium, such as diisopropyl magnesium and dibutyl magnesium, can be obtained, for example, by reacting metal magnesium with a halogenated hydrocarbon or alcohol.

  As the dialkyl glycol ether, at least one of those having a chemical structure represented by the following general formula (1) can be used.

式中、Ｒ₁及びＲ₂は、それぞれ独立して炭素数１〜６のアルキル基及び少なくとも一部の水素がフッ素置換されたアルキル基、フェニル基及び少なくとも一部の水素がハロゲン原子で置換されたフェニル基、並びにシクロヘキシル基及び少なくとも一部の水素がハロゲン原子で置換されたシクロヘキシル基のうちのいずれかである。ｎは１〜１２の整数であり、好ましくは１〜４の整数である。

In the formula, R ₁ and R ₂ are each independently an alkyl group having 1 to 6 carbon atoms, an alkyl group in which at least a part of hydrogen is substituted with fluorine, a phenyl group, and at least a part of hydrogen is substituted with a halogen atom. And a cyclohexyl group and a cyclohexyl group in which at least a part of hydrogen is substituted with a halogen atom. n is an integer of 1 to 12, and preferably an integer of 1 to 4.

Examples of the alkyl group that can constitute R ₁ and R ₂ in the general formula (1) include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a pentyl group, an isopentyl group, and a hexyl group. Etc.

In addition, examples of the phenyl group in which at least a part of hydrogen capable of constituting R ₁ and R ₂ in the general formula (1) is substituted with a halogen atom include a 2-chlorophenyl group, a 3-chlorophenyl group, 4- Chlorophenyl group, 2,4-dichlorophenyl group, 2-bromophenyl group, 3-bromophenyl group, 4-bromophenyl group, 2,4-dibromophenyl group, 2-iodophenyl group, 3-iodophenyl group, 4- Examples include iodophenyl group and 2,4-iodophenyl group.

Furthermore, examples of the cyclohexyl group in which at least a part of hydrogen atoms constituting R ₁ and R ₂ in the general formula (1) are substituted with a halogen atom include a 2-chlorocyclohexyl group, a 3-chlorocyclohexyl group, 4-chlorocyclohexyl group, 2,4-dichlorocyclohexyl group, 2-bromocyclohexyl group, 3-bromocyclohexyl group, 4-bromocyclohexyl group, 2,4-dibromocyclohexyl group, 2-iodocyclohexyl group, 3-iodocyclohexyl Group, 4-iodocyclohexyl group, 2,4-iodocyclohexyl group and the like.

  In this embodiment, the dialkyl glycol ether as a solvent constituting the electrolytic solution 3 has two carbons between two adjacent oxygen atoms in the chemical structure. By having such a chemical structure, an electrolyte solution that can exhibit practically sufficient charge / discharge characteristics in combination with the magnesium compound as a solute, as will be apparent from Examples and the like to be described later. Can do.

  Specifically, examples of the dialkyl glycol ether include ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, pentaethylene glycol dimethyl ether, hexa Ethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, triethylene glycol butyl methyl ether, etc. are used, higher-boiling triethylene glycol dialkyl ether, tetraethylene glycol dialkyl ether, etc. are preferably used, triethylene glycol dimethyl ether, Tiger ethylene glycol dimethyl ether, triethylene glycol butyl methyl ether, etc. are particularly preferably used. Since these dialkyl glycol ethers are excellent in handleability in a dry environment, they can be suitably used. Further, as is clear from the examples described later, the peak current value of the cyclic voltammogram when triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether or triethylene glycol butyl methyl ether is used as the solvent for the electrolytic solution It is improved to about 120 to 190% of the peak current value of the dialkyl glycol ether. From this, among the dialkyl glycol ethers, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, triethylene glycol butyl methyl ether and other triethylene glycol dialkyl ethers or tetraethylene glycol dialkyl ethers and magnesium ions are particularly preferred. The coordinate structure is considered to be optimal for magnesium dissolution and precipitation, and the effect of improving the discharge rate characteristics can be expected.

  The density | concentration of the said magnesium compound in the electrolyte solution 3 should just be a density | concentration which can ensure the electroconductivity required for the electrolyte solution 3, For example, it is preferable that it is 0.1-2 mol / L, 0.5- Particularly preferred is 1 mol / L.

The electrolytic solution 3 may contain an additive such as aluminum chloride (AlCl ₃ ) as long as the ion conductivity and the like of the electrolytic solution 3 are not impaired.

  The electrolyte solution 3 described above can be prepared by dissolving an additive such as aluminum chloride in the dialkyl glycol ether and then mixing and dissolving the magnesium compound.

  In the present embodiment, the laminate outer package 4 may be one in which a heat-fusing resin layer (modified polyolefin film or the like) is provided on at least one surface side of a metal foil such as aluminum or stainless steel, preferably a metal foil. What consists of a metal laminate film of the 3 layer structure in which the resin layer (nylon film etc.) was provided in the other surface side can be used. Note that an adhesive layer (not shown) made of a polyolefin-based polymer or the like is interposed between the laminate outer package 4 and the positive external terminal 25 and the negative external terminal 26.

  The magnesium ion secondary battery 1 according to the present embodiment has a configuration in which the laminate 2 and the electrolytic solution 3 are enclosed in a laminate outer package 4 in which a single metal laminate film is folded in two and the periphery is fused. However, the present invention is not limited to such an embodiment, and the laminate 2 and the electrolytic solution 3 are encapsulated in a laminate outer package 4 in which two metal laminate films are stacked and the peripheral edge is fused. It may have a configuration.

  In the magnesium ion secondary battery 1 according to the present embodiment having the above-described configuration, the positive electrode lead wire 24 attached to the positive electrode 21 is connected to the positive electrode external terminal 25 after the laminate 2 is accommodated in the laminate outer package 4, and the negative electrode The negative electrode lead wire (not shown) attached to 22 is connected to the negative electrode external terminal 26, and the electrolyte solution 3 is filled into the laminate outer package 4 using a vacuum injection device or the like, and the laminate outer package 4 is sealed. Can be manufactured.

  Since the solvent constituting the electrolytic solution 3 in the present embodiment is the above-described dialkyl glycol ether having a relatively high boiling point, when the electrolytic solution 3 is filled and sealed in the laminate outer package 4 using a vacuum injection device or the like. Further, the volatilization of the electrolytic solution 3 is suppressed. Therefore, according to this embodiment, the effect that it becomes possible to manufacture the laminate type magnesium ion secondary battery 1 easily can be achieved.

  As described above, according to the present embodiment, since the dialkyl glycol ether having a relatively high boiling point is used as the solvent constituting the electrolytic solution 3, the heat resistance of the magnesium ion secondary battery 1 can be improved. . Further, as will be apparent from the examples described later, a combination of the dialkyl glycol ether as the solvent and the magnesium compound as the solute in the mixture contained in the electrolytic solution 3 has excellent charge / discharge characteristics. The secondary battery 1 can be obtained. Furthermore, since the solvent constituting the electrolytic solution 3 is the above-described dialkyl glycol ether having a relatively high boiling point, an effect that the laminate-type magnesium ion secondary battery 1 can be easily manufactured can be achieved.

[Magnesium ion secondary battery pack]
Next, a magnesium ion secondary battery pack according to an embodiment of the present invention will be described with reference to the drawings. FIG. 3 is an exploded perspective view showing the magnesium ion secondary battery pack in the present embodiment.

  As shown in FIG. 3, the battery pack 10 includes a plurality of magnesium ion secondary batteries 1 according to the present embodiment housed in a battery case 30, and the battery case 30 includes a resin container 36 a, a resin container 36 b, and an end portion. The case 37 is configured to be stored. Further, a protective circuit board 34 for preventing overcharge and overdischarge is provided between one end face of the battery case 30 and a face including the positive electrode terminal 32 and the negative electrode terminal 33 and the end case 37. It has been. The positive external terminal 25 of each magnesium ion secondary battery 1 is connected to the positive terminal 32 and the negative external terminal 26 is connected to the negative terminal 33.

  The protection circuit board 34 includes an external connection connector 35. The external connection connector 35 is inserted into an external connection window 38a provided in the resin container 36a and an external connection window 38b provided in the end case 37. Connected with external terminals. The protection circuit board 34 is mounted with a charge / discharge safety circuit for controlling charge / discharge, a wiring circuit for connecting the external connection terminal and the magnesium ion secondary battery 1, and the like.

  The battery pack 10 can employ a conventionally known battery pack configuration as appropriate, except that the magnesium ion secondary battery 1 according to the present embodiment is used. For example, the battery pack 10 appropriately includes a positive lead plate connected to the positive terminal 32, a negative lead plate connected to the negative terminal 33, an insulator, and the like between the battery case 30 and the end case 37. Also good.

  In addition, the battery case 30 including the magnesium ion secondary battery 1 according to the present embodiment further includes functions such as overcurrent blocking and battery temperature monitoring in the protection circuit, in addition to the usage mode for the battery pack, and You may use for the aspect formed by integrating the said protection circuit in secondary battery itself. In this aspect, it can be used as a secondary battery having a protection function and a protection circuit without constituting a battery pack, and is highly versatile.

  The embodiment described above is described for facilitating understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

  In the above-described embodiment, the magnesium ion secondary battery 1 includes the stacked body 2 in which a plurality of sheet-like positive electrodes 21 and negative electrodes 22 are alternately stacked with separators 23 interposed therebetween as a power generation element. This invention is not limited to such an aspect, You may provide a pair of positive electrode 21 and negative electrode 22, and the separator 23 located between them as an electric power generation element.

  Moreover, in the said embodiment, although the laminated type magnesium ion secondary battery 1 provided with the laminated exterior body 4 was mentioned as an example, it demonstrated, this invention is not limited to such an aspect, A sheet-like positive electrode A mode in which a wound electrode plate group that is wound in a spiral shape via 21, the negative electrode 22, and the separator 23 is inserted into a battery container (such as a battery can) may be used.

  EXAMPLES Hereinafter, although an Example etc. are given and this invention is demonstrated further in detail, this invention is not limited to the following Example etc. at all.

[Example 1]
<Preparation of electrolyte>
In an inert atmosphere glove box, aluminum chloride (0.177 g) was dissolved in triethylene glycol dimethyl ether (3.72 g), and then dibutyl magnesium (0.28 g) was dissolved to prepare an electrolytic solution.

<Cyclic voltammetry evaluation>
Rod-shaped nickel metal (φ: 0.90 mm, length: 0.8 cm) as a working electrode, rod-shaped magnesium metal (φ: 1.6 mm, length: 0.8 cm) as a counter electrode and a reference electrode, and Using the electrolyte prepared as described above, a three-electrode cell was assembled in a glove box in an inert atmosphere, and cyclic voltammetry evaluation was performed using this as a test cell. Cyclic voltammetry evaluation was performed by sweeping the potential to −1.5 V, then sweeping to 2.7 V, and repeating this operation 30 times. The scanning speed was 10 mV / sec. As a result, it was possible to confirm the precipitation and dissolution of magnesium ions by a stable redox current. The peak current was about 1 mA.

<Preparation of positive electrode>
Molybdenum sulfide (Mo ₆ S ₈ , 5 g), acetylene black (0.3 g), carbon nanotubes (manufactured by Showa Denko KK, VGCF (registered trademark), 0.2 g), KF polymer (6 g) and N-methylpyrrolidone ( NMP, 4 g) was mixed and stirred for 5 minutes at a rotation speed of 8000 rpm using an Excel auto homogenizer (manufactured by Nippon Seiki Seisakusho) to prepare a positive electrode active material layer forming solution.

  Using an applicator having a gap of 200 μm, the positive electrode active material layer forming solution is applied to one side of a copper substrate (thickness: 10 μm) as a current collector, dried at 150 ° C., and 2 ton using a press. A positive electrode was produced by pressing at / cm.

<Production of negative electrode>
A magnesium alloy (AZ31, manufactured by Nippon Metals Co., Ltd., thickness: 45 μm) was prepared and used as a negative electrode.

<Production of laminate cell>
In a sealed container (D-EL40H, manufactured by Dai Nippon Printing Co., Ltd.) composed of a laminate film having a propylene-based polymer layer on one side and a polymer layer on the other side, a separator (# 2500, manufactured by Celgard) ), And a laminated body with the positive electrode and the negative electrode facing each other is inserted, and an electrolytic solution is sealed in a sealed container using a vacuum injection device (VS1616, manufactured by Sank Metal Co., Ltd.), and the configuration shown in FIGS. A laminate type magnesium secondary battery 1 (laminate cell) was prepared. A sealant film (polyolefin polymer, manufactured by Hosen Co., Ltd.) was interposed between the positive electrode external terminal 25 and the negative electrode external terminal 26 and the inside of the sealed container (propylene polymer layer).

<Charge / discharge test>
Using the laminate cell, a charge / discharge test was performed under the conditions of a current density of 6.25 μA / cm ² , a voltage range of 0.3 to 1.7 V, and 10 cycles. As a result, it was confirmed that the discharge capacity was 85 mAh / g, and it could be repeatedly charged and discharged although there was some deterioration.

[Example 2]
<Cyclic voltammetry evaluation>
An electrolyte solution was prepared in the same manner as in Example 1 except that ethylene glycol dimethyl ether (4.32 g) was used instead of triethylene glycol dimethyl ether (3.72 g), and cyclic voltammetry evaluation was performed. As a result, it was possible to confirm the precipitation and dissolution of magnesium ions by a stable redox current. The peak current was about 0.8 mA.

Example 3
<Cyclic voltammetry evaluation>
An electrolytic solution was prepared in the same manner as in Example 1 except that tetraethylene glycol dimethyl ether (3.72 g) was used instead of triethylene glycol dimethyl ether (3.72 g), and cyclic voltammetry evaluation was performed. As a result, it was possible to confirm the precipitation and dissolution of magnesium ions by a stable redox current. The peak current was about 1 mA.

Example 4
<Cyclic voltammetry evaluation>
An electrolytic solution was prepared in the same manner as in Example 1 except that aluminum chloride was not added, and cyclic voltammetry evaluation was performed. As a result, it was possible to confirm the precipitation and dissolution of magnesium ions by a stable redox current. The peak current was about 0.6 mA.

Example 5
<Cyclic voltammetry evaluation>
An electrolytic solution was prepared in the same manner as in Example 1 except that triethylene glycol butyl methyl ether (3.72 g) was used instead of triethylene glycol dimethyl ether (3.72 g), and cyclic voltammetry evaluation was performed. As a result, it was possible to confirm the precipitation and dissolution of magnesium ions by a stable redox current. The peak current was about 1.5 mA.

Example 6
<Preparation of electrolyte>
In an inert atmosphere glove box, aluminum chloride (1.33 g) was dissolved in triethylene glycol dimethyl ether (8.28 g), and then magnesium bis (hexamethyldisilazide) (1.72 g) was dissolved in the electrolysis. A liquid was prepared.

<Cyclic voltammetry evaluation>
Cyclic voltammetry evaluation was performed in the same manner as in Example 1 except that the above electrolytic solution was used. Cyclic voltammetry evaluation was performed by sweeping the potential to −1.5 V, then sweeping to 2.7 V, and repeating this operation 30 times. The scanning speed was 10 mV / sec. As a result, it was possible to confirm the precipitation and dissolution of magnesium ions by a stable redox current. In addition, the decomposition reaction of the electrolytic solution due to the oxidation potential did not occur.

<Charge / discharge test>
A laminate cell was produced in the same manner as in Example 1 except that the electrolytic solution was used, and a charge / discharge test was performed in the same manner as in Example 1 using the laminate cell. As a result, the discharge capacity was 42.4 mAh / g, and it was confirmed that charging and discharging were possible repeatedly, although there was some deterioration.

[Comparative Example 1]
<Cyclic voltammetry evaluation>
An electrolyte solution was prepared in the same manner as in Example 1 except that tetrahydrofuran (4.12 g) was used instead of triethylene glycol dimethyl ether (3.72 g), and cyclic voltammetry evaluation was performed. As a result, it was possible to confirm the precipitation and dissolution of magnesium ions. The peak current was about 0.025 mA.

<Charge / discharge test>
A laminate cell was produced in the same manner as in Example 1 except that an electrolytic solution in which triethylene glycol dimethyl ether (3.72 g) was replaced with tetrahydrofuran (4.12 g) was used. However, when the electrolytic solution is sealed, the electrolyte is volatilized, and a laminate cell that can obtain a stable voltage cannot be manufactured.

[Comparative Example 2]
<Cyclic voltammetry evaluation>
An electrolytic solution was prepared in the same manner as in Example 1 except that dimethoxymethane (4.32 g) was used instead of triethylene glycol dimethyl ether (3.72 g), and cyclic voltammetry evaluation was performed. As a result, it was possible to confirm the precipitation and dissolution of magnesium ions. The peak current was about 0.006 mA.

<Charge / discharge test>
A laminate cell was produced in the same manner as in Example 1 except that an electrolytic solution in which triethylene glycol dimethyl ether (3.72 g) was replaced with dimethoxymethane (4.32 g) was used. However, when the electrolytic solution is sealed, the electrolyte is volatilized, and a laminate cell that can obtain a stable voltage cannot be manufactured.

[Comparative Example 3]
<Cyclic voltammetry evaluation>
An electrolytic solution was prepared in the same manner as in Example 1 except that methylpropyl ether (5.18 g) was used instead of triethylene glycol dimethyl ether (3.72 g), and cyclic voltammetry evaluation was performed. As a result, it was possible to confirm the precipitation and dissolution of magnesium ions. The peak current was about 0.15 mA.

<Charge / discharge test>
A laminate cell was produced in the same manner as in Example 1 except that an electrolytic solution in which triethylene glycol dimethyl ether (3.72 g) was replaced with methyl propyl ether (5.18 g) was used. However, when the electrolytic solution is sealed, the electrolyte is volatilized, and a laminate cell that can obtain a stable voltage cannot be manufactured.

[Comparative Example 4]
<Preparation of electrolyte>
In an inert atmosphere glove box, aluminum chloride (0.022 g) was dissolved in triethylene glycol dimethyl ether (4.98 g), and then magnesium chloride (0.024 g) was dissolved to prepare an electrolytic solution.

<Cyclic voltammetry evaluation>
A three-electrode cell was prepared in the same manner as in Example 1 except that the above electrolytic solution was used, and cyclic voltammetry evaluation was performed. As a result, magnesium ion precipitation and dissolution could not be confirmed.

[Comparative Example 5]
<Cyclic voltammetry evaluation>
An electrolytic solution was prepared in the same manner as in Example 1 except that 1,4-diethoxybutane (3.72 g) was used instead of triethylene glycol dimethyl ether (3.72 g), and cyclic voltammetry evaluation was performed. As a result, magnesium ion precipitation and dissolution could not be confirmed.

[Comparative Example 6]
<Cyclic voltammetry evaluation>
An electrolytic solution was prepared in the same manner as in Example 1 except that 1,5-dimethoxypentane (3.72 g) was used instead of triethylene glycol dimethyl ether (3.72 g), and cyclic voltammetry evaluation was performed. As a result, magnesium ion precipitation and dissolution could not be confirmed.

[Comparative Example 7]
<Cyclic voltammetry evaluation>
An electrolytic solution was prepared in the same manner as in Example 1 except that 1,6-dimethoxyhexane (3.72 g) was used instead of triethylene glycol dimethyl ether (3.72 g), and cyclic voltammetry evaluation was performed. As a result, magnesium ion precipitation and dissolution could not be confirmed.

[Comparative Example 8]
<Preparation of electrolyte>
In an inert atmosphere glove box, aluminum chloride (1.33 g) was dissolved in tetrahydrofuran (7.48 g), and then phenylmagnesium chloride (27% tetrahydrofuran solution, 2.52 g) was dissolved to prepare an electrolytic solution. .

<Cyclic voltammetry evaluation>
A three-electrode cell was prepared in the same manner as in Example 1 except that the above electrolytic solution was used, and cyclic voltammetry evaluation was performed. As a result, it was possible to confirm the precipitation and dissolution of magnesium ions. However, decomposition of the electrolytic solution started around an oxidation potential of 1.8V.

<Charge / discharge test>
A laminate cell was produced in the same manner as in Example 1 except that the above electrolytic solution was used. However, when the container in which the electrolytic solution is sealed is opened in a dry environment, the electrolytic solution has been altered. In addition, the electrolyte volatilizes when the electrolytic solution is sealed, and a laminate cell that can obtain a stable voltage cannot be manufactured.

[Comparative Example 9]
<Preparation of electrolyte>
In an inert atmosphere glove box, aluminum chloride (1.33 g) was dissolved in an appropriate amount of tetrahydrofuran, and then phenylmagnesium chloride (27% tetrahydrofuran solution, 2.52 g) was dissolved. Thereafter, triethylene glycol dimethyl ether (4.32 g) was added, and tetrahydrofuran was completely removed using an organic solvent concentration recovery apparatus (Soltramini, manufactured by Techno Sigma) to prepare an electrolytic solution.

<Cyclic voltammetry evaluation>
A three-electrode cell was prepared in the same manner as in Example 1 except that the above electrolytic solution was used, and cyclic voltammetry evaluation was performed. As a result, magnesium ion precipitation and dissolution could not be confirmed.

  As described above, the electrolyte solution of Examples 1 to 5 (the electrolyte solution including a mixture of a predetermined dialkyl glycol ether (dialkyl glycol ether having two carbons between two adjacent oxygen atoms in the compound) and dialkyl magnesium) In the magnesium ion secondary battery using, the precipitation and dissolution of magnesium ions can be confirmed by cyclic voltammetry evaluation, and the peak current is high, and it is confirmed that the battery characteristics are sufficient. In particular, in Examples 1, 3, and 5 using triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether or triethylene glycol butyl methyl ether as the electrolyte solution solvent, the peak current is higher, and excellent battery characteristics are exhibited. confirmed.

  In addition, in the magnesium ion secondary battery using the electrolyte solution of Example 6 (electrolyte solution using magnesium bis (hexamethyldisilazide) as a solute), magnesium ions are precipitated and dissolved by cyclic voltammetry evaluation. It was confirmed that the battery exhibited sufficient battery characteristics. In particular, an electrolytic solution obtained by combining triethylene glycol dimethyl ether as a solvent and magnesium bis (hexamethyldisilazide) as a solute does not cause a decomposition reaction due to an oxidation potential, and is used as an electrolytic solution for a magnesium ion secondary battery. It was confirmed that a magnesium ion secondary battery having a high energy density can be provided by using it.

  On the other hand, the electrolyte solution of Comparative Examples 1 to 3 (an electrolyte solution using an organic ether other than a predetermined dialkyl glycol ether (dialkyl glycol ether having two carbons between two adjacent oxygen atoms in the compound) as a solvent) is used. In the magnesium ion secondary battery, although the precipitation and dissolution of magnesium ions could be confirmed by cyclic voltammetry evaluation, it was confirmed that the peak current was low and the battery characteristics were inferior. In the magnesium ion secondary battery using the electrolytic solution of Comparative Example 4 (electrolytic solution using magnesium chloride as a solute), magnesium ion precipitation and dissolution could not be confirmed by cyclic voltammetry evaluation.

  Moreover, the electrolyte solution of Comparative Examples 5-7 (electrolyte solution using a dialkyl glycol ether having three or more carbons between two adjacent oxygen atoms in the compound as a solvent) and the electrolyte solution of Comparative Example 9 (dialkyl glycol ether) In a magnesium ion secondary battery using an electrolyte solution in which a magnesium compound having two different ligands bonded to a magnesium atom is used as a solute, the magnesium ion is precipitated and dissolved by cyclic voltammetry evaluation. I could not confirm.

  Furthermore, in the magnesium ion secondary battery using the electrolyte solution of Comparative Example 8 (electrolyte solution using tetrahydrofuran as a solvent), although the magnesium ion deposition and dissolution could be confirmed by cyclic voltammetry evaluation, It became clear that the electrolytic solution started to decompose at the electric potential (about 1.8 V). That is, when the electrolyte solution of Comparative Example 8 is used as an electrolyte solution for a magnesium ion secondary battery, the operating voltage must be 1.8 V or less in the magnesium ion secondary battery, and it is difficult to improve the energy density. It became clear that there was.

  From this result, a predetermined magnesium compound (bonded to a magnesium atom) as a solute in a predetermined dialkyl glycol ether (dialkyl glycol ether having two carbons between two adjacent oxygen atoms in the compound) as a solvent constituting the electrolytic solution. It was revealed that a magnesium ion secondary battery having good characteristics can be configured by combining two magnesium ligands having the same ligand.

  In Example 1, it was possible to produce a laminate cell without causing the electrolyte solution to volatilize. However, in Comparative Examples 1 to 3 and 8, it was possible to produce a laminate cell because the electrolyte solution was volatilized. could not. From this result, by using dialkyl glycol ether (dialkyl glycol ether having two carbons between two adjacent oxygen atoms in the compound) as a solvent constituting the electrolytic solution, in the vacuum sealing step in the manufacturing process of the laminate cell It was confirmed that the volatilization of the electrolyte solution can be suppressed. Moreover, since the stability of the electrolyte solution in a dry environment can be improved, it is considered that industrial production of a magnesium ion secondary battery is possible in a production line in a dry environment.

  From the above results, by using the above-mentioned dialkyl glycol ether having a high boiling point as a solvent constituting the electrolytic solution, a magnesium ion secondary battery having excellent heat resistance and handling property can be obtained, and predetermined magnesium as a solute. It has been clarified that a compound (a magnesium compound in which two ligands bonded to a magnesium atom have the same molecular structure) exhibit good charge / discharge characteristics.

  Furthermore, by using the above-mentioned dialkyl glycol ether having a high boiling point as an electrolyte solution solvent, it is possible to suppress the evaporation of the electrolyte solution in the vacuum sealing step in the production process of the laminate cell. It became clear that a type of magnesium ion secondary battery could be produced.

DESCRIPTION OF SYMBOLS 1 ... Magnesium ion secondary battery 21 ... Positive electrode 22 ... Negative electrode 3 ... Electrolytic solution 4 ... Laminate exterior body 10 ... Battery pack (magnesium ion secondary battery pack)

Claims (18)

A magnesium ion secondary battery having a positive electrode, a negative electrode, and an electrolyte solution,
The electrolytic solution includes a mixture of a dialkyl glycol ether represented by the following general formula (1) and a magnesium compound in which two identical ligands are bonded to a magnesium atom,
The magnesium ion secondary battery, wherein the ligand has a hydrophobic structure at a position farthest from the magnesium atom.

In the formula, R ₁ and R ₂ are each independently an alkyl group having 1 to 6 carbon atoms, an alkyl group in which at least a part of hydrogen is substituted with fluorine, a phenyl group, and at least a part of hydrogen is substituted with a halogen atom. And a phenyl group, a cyclohexyl group, and a cyclohexyl group in which at least a part of hydrogen is substituted with a halogen atom, and n is an integer of 1 to 12.   2. The ligand has any one of an alkyl group having 1 to 6 carbon atoms and the alkyl group in which at least a part of hydrogen is fluorine-substituted at a position farthest from the magnesium atom. The magnesium ion secondary battery described in 1.   The magnesium ion secondary battery according to claim 1 or 2, wherein the magnesium compound is formed by bonding two disilazane groups to the magnesium atom.   The magnesium ion secondary battery according to any one of claims 1 to 3, wherein the magnesium compound is magnesium bis (hexamethyldisilazide).   The magnesium ion secondary battery according to claim 1 or 2, wherein the magnesium compound is diisopropyl magnesium or dibutyl magnesium.   The dialkyl glycol ether is ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, pentaethylene glycol dimethyl ether, hexaethylene glycol dimethyl ether, polyethylene glycol dimethyl ether or triethylene glycol butyl methyl ether. The magnesium ion secondary battery in any one of Claims 1-5.   The magnesium ion secondary battery according to any one of claims 1 to 6, wherein the dialkyl glycol ether is triethylene glycol dialkyl ether or tetraethylene glycol dialkyl ether.   The magnesium ion secondary battery according to any one of claims 1 to 7, wherein the dialkyl glycol ether is triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, or triethylene glycol butyl methyl ether.   The magnesium ion secondary battery according to any one of claims 1 to 8, wherein the positive electrode, the negative electrode, and the electrolytic solution are sealed in a laminate outer package. A mixture of a dialkyl glycol ether represented by the following general formula (1) and a magnesium compound in which two identical ligands are bonded to a magnesium atom;
The electrolyte for a magnesium ion secondary battery, wherein the ligand has a hydrophobic structure at a position farthest from the magnesium atom.

In the formula, R ₁ and R ₂ are each independently an alkyl group having 1 to 6 carbon atoms, an alkyl group in which at least a part of hydrogen is substituted with fluorine, a phenyl group, and at least a part of hydrogen is substituted with a halogen atom. And a phenyl group, a cyclohexyl group, and a cyclohexyl group in which at least a part of hydrogen is substituted with a halogen atom, and n is an integer of 1 to 12.   The ligand has any one of an alkyl group having 1 to 6 carbon atoms and the alkyl group in which at least a part of hydrogen is fluorine-substituted at a position farthest from the magnesium atom. Electrolyte for magnesium ion secondary batteries as described in 2.   The electrolyte for magnesium ion secondary battery according to claim 10 or 11, wherein the magnesium compound is formed by bonding two disilazane groups to the magnesium atom.   The said magnesium compound is magnesium bis (hexamethyldisilazide), The electrolyte solution for magnesium ion secondary batteries in any one of Claims 10-12 characterized by the above-mentioned.   The said magnesium compound is diisopropyl magnesium or dibutyl magnesium, The electrolyte solution for magnesium ion secondary batteries of Claim 10 or 11 characterized by the above-mentioned.   The dialkyl glycol ether is ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, pentaethylene glycol dimethyl ether, hexaethylene glycol dimethyl ether, polyethylene glycol dimethyl ether or triethylene glycol butyl methyl ether. The electrolyte solution for magnesium ion secondary batteries in any one of Claims 10-14.   The electrolyte solution for magnesium ion secondary batteries according to any one of claims 10 to 15, wherein the dialkyl glycol ether is triethylene glycol dialkyl ether or tetraethylene glycol dialkyl ether.   The electrolyte solution for magnesium ion secondary batteries according to any one of claims 10 to 16, wherein the dialkyl glycol ether is triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, or triethylene glycol butyl methyl ether.   A storage case, a magnesium ion secondary battery according to any one of claims 1 to 9, and a protection circuit including an overcharge protection function and an overdischarge protection function, wherein the magnesium ion secondary battery is provided in the storage case. And a magnesium ion secondary battery pack, wherein the protection circuit is housed.

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