WO2015105140A1

WO2015105140A1 - Secondary battery

Info

Publication number: WO2015105140A1
Application number: PCT/JP2015/050360
Authority: WO
Inventors: 哲市坪; 松原　英一郎; 俊介八木; 邦明邑瀬; 北田　敦
Original assignee: 国立大学法人京都大学; 公立大学法人大阪府立大学
Priority date: 2014-01-08
Filing date: 2015-01-08
Publication date: 2015-07-16
Also published as: JPWO2015105140A1

Abstract

A secondary battery is provided with a negative electrode, a positive electrode, and an electrolyte solution that is interposed between the positive electrode and the negative electrode. The positive electrode contains a cluster compound that comprises a cluster that is represented by formula (1) (in the formula, the six M each independently represent a chrome atom, a molybdenum atom, or a tungsten atom, and each A independently represents a chalcogen atom). The electrolyte solution contains a fluid that makes it possible for carrier ions to be transferred between the positive electrode and the negative electrode. The entry of the fluid into gaps in the atomic arrangement structure of the cluster compound is minimized.

Description

Secondary battery

The present invention relates to a secondary battery. More specifically, the present invention relates to a secondary battery that can be suitably used as a power source for transportation equipment, mobile equipment, and the like; a secondary battery for storing power. Since the secondary battery of the present invention can secure a high electromotive force, the secondary battery for transportation equipment such as an aircraft, a hybrid vehicle, and an electric vehicle; the secondary battery for mobile equipment; and the secondary battery for storing power. It is expected to be used for secondary batteries.

In recent years, there has been a demand for higher performance of power storage devices such as secondary batteries from the viewpoint of optimization of energy supply and demand and reduction of environmental load. Therefore, improvement of the energy density of the electricity storage device is attempted. Currently, lithium ion secondary batteries can be used as power storage devices for transportation equipment, mobile devices, power storage, etc., because they can ensure high voltage and have high energy density among power storage devices. It has been. However, the lithium ion secondary battery may cause oxidative decomposition of the positive electrode active material due to overcharge.

On the other hand, a magnesium secondary battery including a positive electrode containing a chevrel compound as a positive electrode active material and an electrolytic solution made of a solution obtained by dissolving a Grignard reagent and aluminum chloride in tetrahydrofuran has been proposed (for example, see Non-Patent Document 1). ).

However, the magnesium secondary battery described in Non-Patent Document 1 has a drawback that it can obtain only an electromotive force that is practically insufficient and has a small charge capacity per unit mass.

This invention is made | formed in view of the said prior art, and makes it a subject to provide the secondary battery which can ensure a higher electromotive force.

In one aspect, the present invention comprises a negative electrode, a positive electrode, and an electrolyte solution interposed between the positive electrode and the negative electrode,
The positive electrode has the formula (I):

(In the formula, 6 M's are each independently a chromium atom, a molybdenum atom or a tungsten atom, and A's are each independently a chalcogen atom)
An electrode including a cluster compound having a cluster represented by:
The electrolytic solution is an electrolytic solution containing a liquid capable of transferring carrier ions between the positive electrode and the negative electrode,
The present invention relates to a secondary battery characterized in that the liquid is prevented from entering the voids of the atomic arrangement structure of the cluster compound. The secondary battery according to the present embodiment includes a positive electrode including the cluster compound, and the liquid intrusion into the void of the atomic arrangement structure of the cluster compound is suppressed. Insertion and desorption of carrier ions from the positive electrode are not hindered by the liquid and are performed smoothly. Therefore, according to the secondary battery according to the present embodiment, a high electromotive force can be ensured.

In the secondary battery according to the present embodiment, the liquid may be an ionic liquid or a mixture obtained by mixing at least two kinds of ionic liquids. In this case, the ionic liquid is an ionic liquid containing an anion having a halogen atom and an organic cation or a metal cation, because the charge / discharge reaction in the negative electrode can be performed more efficiently and a higher electromotive force can be secured. It is preferable. Furthermore, since the ionic liquid can perform charge / discharge reaction in the negative electrode more efficiently and secure a higher electromotive force, as the anion, a non-coordinating halide anion, a metal halide complex anion, formula (III) :

(Wherein X ² represents a halogen atom and q represents a number of 1 to 2)
A halogenoamate anion represented by formula (IV):

(Wherein R ¹ and R ² each independently represents a halogen atom or a C 1-8 alkyl group having a halogen atom)
A sulfonylamide anion represented by formula (V):

(Wherein R ³ represents a halogen atom or an alkyl group having 1 to 8 carbon atoms having the halogen atom)
And an anion selected from the group consisting of sulfonate anions represented by formula (VII):

(Wherein R ⁴ , R ⁵ , R ⁶ and R ⁷ each independently represents an optionally substituted alkyl group having 1 to 8 carbon atoms or an alkyloxyalkyl group having 1 to 8 carbon atoms) )
A quaternary ammonium cation represented by formula (VIII):

(Wherein R ⁸ and R ⁹ are each independently an alkyl group having 1 to 8 carbon atoms, Y represents a direct bond or a methylene group)
A cation represented by formula (IX):

(Wherein R ¹⁰ and R ¹¹ each independently represents an alkyl group having 1 to 8 carbon atoms)
And an imidazolium cation represented by the formula (X):

(Wherein R ¹² represents an alkyl group having 1 to 8 carbon atoms)
An ionic liquid containing a cation selected from the group consisting of pyridinium cations represented by

Also, in the secondary battery according to the present embodiment, the liquid may be a compound having a bulky enough to prevent the cluster compound from entering the voids of the atomic arrangement structure. In this case, the compound is preferably a glycol ether compound because the compound has a sufficient bulkiness to suppress the entry of the atomic arrangement structure of the cluster compound into the voids.

In the secondary battery according to the present embodiment, the cluster compound is preferably a chevrel compound from the viewpoint of securing a higher mass energy density. In this case, the chevrel compound has the formula (II):

(In the formula, each p ¹ is independently an alkali metal atom, an alkaline earth metal atom, a group 12 typical metal atom, a group 13 typical metal atom, a group 14 typical metal atom, a 3d transition metal atom, or a 4d transition metal. Atoms, 6 M are the same as above, A is the same as above, p is a number from 0 to 4)
The chevrel compound which has the composition represented by these may be sufficient.

According to the multivalent metal secondary battery of the present invention, there is an excellent effect that a higher electromotive force can be secured.

In Experimental Example 1, an X-ray diffraction diagram showing the results of examining the X-ray diffraction powder Mo ₆ S ₈ cluster compound (Sample A) and Mo ₆ S ₈ cluster compound containing tetrahydrofuran (Sample B). In Experimental example 2, it is an X-ray-diffraction figure which shows the result of having investigated the X-ray diffraction of the powder (sample A) of a copper chevrel compound, and the copper chevrel compound containing tetrahydrofuran (sample B). 2 is a schematic explanatory diagram illustrating a configuration of a three-electrode cell in Example 1. FIG. In Test Example 1, a working electrode in the case of using an electrolytic solution containing PP13-TFSI and Mg (TFSI) ₂ , a working electrode having a Mo ₆ S ₈ cluster compound as an active material, and a counter electrode made of a magnesium sheet It is a graph which shows the result of having investigated the relationship between terminal potential of this and electric current. In Test Example 2, it is an X-ray diffraction diagram showing the results of examining the X-ray diffraction of the active material of the working electrode after discharge. It is a schematic explanatory drawing which shows the structure of the beaker cell in Example 2. FIG. (A) is a graph showing the results of examining time-dependent changes in the terminal potential and current of the working electrode in Test Example 3, and (B) is a time-dependent change in the electric capacity of the beaker cell in Test Example 3. It is a graph which shows a result. (A) is the measurement target portion of the positive electrode active material existing in the positive electrode after discharge used in SEM-EDX analysis in Test Example 4, and (b) is used in SEM-EDX analysis in Test Example 4. It is a drawing substitute photograph which shows the measurement object part of the non-existing location of the positive electrode active material in the positive electrode after discharge. In Experiment 4, it is an X-ray diffraction diagram which shows the result of having investigated the X-ray diffraction of the positive electrode active material which exists in the positive electrode after discharge. In Experiment 4, it is a graph which shows the result of having investigated ratio (composition ratio) of each element of the location where a positive electrode active material exists with respect to the quantity of each element of the location where the positive electrode active material does not exist in the positive electrode after discharge. In Test Example 5, an electrolytic solution containing P13-TFSI and Mg (TFSI) ₂ , a positive electrode having a Mo ₆ S ₈ cluster compound as an active material, and a negative electrode having Mg ₂ Sn / Sn as an active material were used. Cyclic voltammogram of the case. In Test Example 6, an electrolytic solution containing P13-TFSI and Mg (TFSI) ₂ , a positive electrode having a Mo ₆ S ₈ cluster compound as an active material, and a negative electrode having Mg ₂ Sn / Sn as an active material were used. It is a graph which shows the result of having investigated the charge / discharge characteristic in a case. In Test Example 7, an electrolytic solution containing Cs-TFSI, Li-TFSI, and Mg (TFSI) ₂ , a working electrode having Cu ₂ Mo ₆ S ₈ as an active material, and a counter electrode made of a magnesium sheet were used. It is a graph which shows the result of having investigated the relationship between the terminal potential of a working electrode at the time of performing cyclic voltammetry at 180 degreeC, and an electric current. In Test Example 8, an electrolytic solution containing Cs-TFSI, Li-TFSI, and Mg (TFSI) ₂ , a working electrode having Cu ₂ Mo ₆ S ₈ as an active material, and a counter electrode made of a lithium sheet were used. It is a graph which shows the result of having investigated the relationship between the terminal potential of a working electrode at the time of performing cyclic voltammetry at 150 degreeC, and an electric current. In Test Example 8, an electrolytic solution containing Cs-TFSI, Li-TFSI and Mg (TFSI) ₂ , a working electrode having a Mo ₆ S ₈ cluster compound as an active material, and a counter electrode comprising a counter electrode made of a lithium sheet It is a graph which shows the result of having investigated the relationship between the terminal electric potential of a working electrode at the time of performing cyclic voltammetry at 150 degreeC, and electric current. It is a schematic explanatory drawing which shows the structure of the beaker cell in Example 6. FIG. In Test Example 10, an electrolytic solution containing Cs-TFSI, Li-TFSI, and Mg (TFSI) ₂ , a positive electrode having a Mo ₆ S ₈ cluster compound as an active material, and a negative electrode having Mg ₂ Sn / Sn as an active material It is a graph which shows the result of having investigated the charge / discharge characteristic at the time of using. (A) is a graph showing the results of examining time-dependent changes in the terminal potential and current of the working electrode in Test Example 10, and (B) is a graph showing the results of examining time-dependent changes in the electric capacity of the beaker cell. is there. (A) is the measurement target part of the location of the positive electrode active material in the positive electrode after discharge used in SEM-EDX analysis in Test Example 11, and (b) is used in SEM-EDX analysis in Test Example 11. It is a drawing substitute photograph which shows the measurement object part of the non-existing location of the positive electrode active material in the positive electrode after discharge. In Experiment 11, it is an X-ray diffraction diagram which shows the result of having investigated the X-ray diffraction of the positive electrode active material of each of the positive electrode after charge, and the positive electrode after discharge. In Experiment 11, it is an X-ray diffraction diagram which shows the result of having investigated the X-ray diffraction of the positive electrode active material of each of the positive electrode after charge, and the positive electrode after discharge. In Experiment 11, it is a graph which shows the result of having investigated ratio (composition ratio) of each element of the location where a positive electrode active material exists with respect to the quantity of each element of the location where the positive electrode active material does not exist in the positive electrode after discharge. In Test example 12, it is a graph which shows the result of having investigated the relationship between the electric potential and current density at the time of using the three-electrode-type cell obtained in Example 7 and Example 8. FIG. In Test Example 13, it is a cyclic voltammogram when using the three-electrode cell obtained in Example 9. FIG. 25 is a cyclic voltammogram showing the result of converting the relationship between the potential and current shown in FIG. 24 to the Mg ²⁺ / Mg standard. In Test example 14, it is a graph which shows the result of having investigated the relationship between the terminal potential of a working electrode at the time of using the three-electrode-type cell obtained in Experimental example 3, and an electric current. In Test example 14, it is a graph which shows the result of having investigated the relationship between the terminal potential of a working electrode at the time of using the three-electrode-type cell obtained in Experimental example 4, and an electric current.

In one aspect, the present invention includes a positive electrode, a negative electrode, and an electrolyte solution interposed between the positive electrode and the negative electrode, wherein the positive electrode has the formula (I):

(In the formula, 6 M's are each independently a molybdenum atom, a chromium atom or a tungsten atom, and A is a chalcogen atom)
An electrode including a cluster compound having a cluster represented by:
The electrolytic solution is an electrolytic solution containing a liquid capable of transferring carrier ions between the positive electrode and the negative electrode,
The present invention relates to a secondary battery characterized in that intrusion of the solvent into the voids of the atomic arrangement structure of the cluster compound is suppressed.

The secondary battery according to the present embodiment includes a positive electrode including the cluster compound, and the liquid is prevented from entering the voids of the atomic arrangement structure of the cluster compound. Therefore, in the secondary battery according to this embodiment, the insertion of carrier ions into the gap and the detachment of carrier ions from the positive electrode are not hindered by the liquid and can be performed smoothly. Therefore, according to the secondary battery according to the present embodiment, carrier ions can be efficiently inserted into and removed from the voids in the atomic arrangement structure of the cluster compound constituting the positive electrode active material of the positive electrode. Therefore, a high electromotive force can be secured.

The positive electrode is an electrode including a cluster compound having a cluster represented by the formula (I). The cluster compound has a cluster represented by the formula (I). The cluster is a cluster in which the binding force of cations as carrier ions is weak. Therefore, a cation as a carrier ion can easily move within the atomic arrangement structure of the cluster compound. Therefore, since the secondary battery according to this embodiment includes the positive electrode including the cluster compound, a charge / discharge reaction at a high potential can be performed.

In formula (I), six M's each independently represent a chromium atom, a molybdenum atom or a tungsten atom. In the cluster compound having the cluster represented by the formula (I), the chromium atom, the molybdenum atom, and the tungsten atom maintain the atomic arrangement structure of the cluster compound and behave electrochemically in the same manner. Among the M, from the viewpoint of securing a higher mass energy density, a chromium atom and a molybdenum atom are preferable, and a chromium atom is more preferable.

In the formula (I), A is a chalcogen atom. Examples of the chalcogen atom include a sulfur atom, a selenium atom, and a tellurium atom. These chalcogen atoms have properties similar to each other, and in the cluster compound having a cluster represented by the formula (I), the atomic arrangement structure of the cluster compound is maintained, and the electrochemically similar behavior to each other is maintained. Indicates. The eight A's may each independently be a sulfur atom, a selenium atom or a tellurium atom. Among the chalcogen atoms, from the viewpoint of securing a higher mass energy density, a sulfur atom and a selenium atom are preferable, and a sulfur atom is more preferable.

Specific examples of the cluster represented by the formula (I) include Mo ₆ S ₈ cluster, Mo ₅ CrS ₈ cluster, Mo ₄ Cr ₂ S ₈ cluster, Mo ₃ Cr ₃ S ₈ cluster, and Mo ₂ Cr. ₄ S ₈ cluster, MoCr ₅ S ₈ cluster, Mo ₆ Se ₈ cluster, Mo ₅ CrSe ₈ cluster, Mo ₄ Cr ₂ Se ₈ cluster, Mo ₃ Cr ₃ Se ₈ cluster, Mo ₂ Cr ₄ Se ₈ cluster, MoCr ₅ Se ₈ clusters, Mo ₆ Te ₈ clusters, Mo ₅ CrTe ₈ clusters, Mo ₄ Cr ₂ Te ₈ clusters, Mo ₃ Cr ₃ Te ₈ clusters, Mo ₂ Cr ₄ Te ₈ clusters, MoCr ₅ Te ₈ clusters, Mo ₅ WS ₈ clusters , Mo ₄ W ₂ S ₈ cluster, Mo ₃ W ₃ S ₈ cluster, Mo ₂ W ₄ S ₈ cluster, MoW ₅ S ₈ class , Mo ₆ Se ₈ cluster, Mo ₅ WSe ₈ cluster, Mo ₄ W ₂ Se ₈ cluster, Mo ₃ W ₃ Se ₈ cluster, Mo ₂ W ₄ Se ₈ cluster, MoW ₅ Se ₈ cluster, Mo ₆ Te ₈ cluster, Mo ₅ WTe ₈ cluster, Mo ₄ W ₂ Te ₈ cluster, Mo ₃ W ₃ Te ₈ cluster, Mo ₂ W ₄ Te ₈ cluster, MoW ₅ Te ₈ cluster, Mo ₄ CrWS ₈ cluster, Mo ₃ Cr ₂ WS ₈ cluster, Mo ₃ CrW ₂ S ₈ cluster, Mo ₂ Cr ₃ WS ₈ cluster, Mo ₂ Cr ₂ W ₂ S ₈ cluster, Mo ₂ CrW ₃ S ₈ cluster, MoCr ₄ WS ₈ cluster, MoCr ₃ W ₂ S ₈ cluster, MoCr ₂ W ₃ S ₈ cluster, MoCrW ₄ S ₈ cluster, Mo ₄ CrWSe ₈ cluster, Mo ₃ Cr ₂ WSe ₈ cluster Mo ₃ CrW ₂ Se ₈ cluster, Mo ₂ Cr ₃ WSe ₈ _{_{_{cluster, Mo 2 Cr 2 W 2 Se}}} 8 cluster, Mo ₂ CrW ₃ Se ₈ cluster, MoCr ₄ WSe ₈ cluster, MoCr ₃ W ₂ Se ₈ cluster, MoCr ₂ W ₃ Se ₈ cluster, MoCrW ₄ Se ₈ cluster, Mo ₄ Cr WTe ₈ cluster, Mo ₃ Cr ₂ WTe ₈ cluster, Mo ₃ CrW ₂ Te ₈ cluster, Mo ₂ Cr ₃ WTe ₈ cluster, Mo ₂ Cr ₂ W ₂ Te ₈ Cluster, Mo ₂ CrW ₃ Te ₈ cluster, MoCr ₄ WTe ₈ cluster, MoCr ₃ W ₂ Te ₈ cluster, MoCr ₂ W ₃ Te ₈ cluster, MoCrW ₄ Te ₈ cluster, Cr ₆ S ₈ cluster, Cr ₅ WS ₈ cluster, Cr ₄ W ₂ S ₈ cluster, Cr ₃ W ₃ S ₈ cluster, Cr ₂ W ₄ S ₈ clusters, CrW ₅ S ₈ clusters, Cr ₆ Se ₈ clusters, Cr ₅ WSe ₈ clusters, Cr ₄ W ₂ Se ₈ clusters, Cr ₃ W ₃ Se ₈ clusters, Cr ₂ W ₄ Se ₈ clusters, CrW ₅ Se ₈ clusters , Cr ₆ Te ₈ cluster, Cr ₅ WTe ₈ cluster, Cr ₄ W ₂ Te ₈ cluster, Cr ₃ W ₃ Te ₈ cluster, Cr ₂ W ₄ Te ₈ cluster, CrW ₅ Te ₈ cluster, and the like. Is not limited to such examples. Among these clusters, Mo ₆ S ₈ cluster, Mo ₅ CrS ₈ cluster, Mo ₄ Cr ₂ S ₈ cluster, and Mo ₃ Cr ₃ S are used from the viewpoint of ensuring sufficient chemical stability and higher mass energy density. _Eight clusters, Mo ₂ Cr ₄ S ₈ clusters and MoCr ₅ S ₈ clusters are preferred.

The cluster compound may have a cluster represented by the formula (I) and further have a cation. Examples of the cluster compound include a chevrel compound; a Mo ₆ S ₈ compound having iron, gallium, silver, cadmium, indium, tin, lead and the like as a cation, but the present invention is limited only to such examples. It is not something.

The chevrel compound has the formula (II):

(In the formula, each p ¹ is independently an alkali metal atom, an alkaline earth metal atom, a group 12 typical metal atom, a group 13 typical metal atom, a group 14 typical metal atom, a 3d transition metal atom, or a 4d transition metal. Atoms, 6 M are the same as above, A is the same as above, p is a number from 0 to 4)
The chevrel compound which has a composition represented by these is mentioned.

In the formula (II), p X ^{1 s} independently represent an alkali metal atom, an alkaline earth metal atom, a group 12 typical metal atom, a group 13 typical metal atom, a group 14 typical metal atom, or a 3d transition metal atom. Or a 4d transition metal atom. These alkali metal atoms, alkaline earth metal atoms, Group 12 typical metal atoms, Group 13 typical metal atoms, Group 14 typical metal atoms, 3d transition metal atoms, and 4d transition metal atoms are atoms that can form a Chevrel phase. High electromotive force and high capacity can be secured. Examples of the alkali metal atom include a lithium atom, a sodium atom, and a potassium atom, but the present invention is not limited to such illustration. Examples of the alkaline earth metal atom include a magnesium atom and a calcium atom, but the present invention is not limited to such illustration. Examples of the group 12 typical metal atom include a zinc atom and a cadmium atom, but the present invention is not limited to such examples. Examples of the group 13 typical metal atom include an aluminum atom, a gallium atom, and an indium atom, but the present invention is not limited to such examples. Examples of the group 14 typical metal atom include a tin atom and a lead atom, but the present invention is not limited to such illustration. Examples of the 3d transition metal atom include an iron atom, a cobalt atom, a nickel atom, and a copper atom. However, the present invention is not limited to such examples. Examples of the 4d transition metal atom include silver, but the present invention is not limited to such examples. X ¹ can be appropriately selected according to the type of secondary battery, the use of the secondary battery, and the like. Among X ^1, from the viewpoint of constructing a rocking chair type battery having a high electromotive force and high capacity, lithium atom, sodium atom, a magnesium atom, a zinc atom, cadmium atom, aluminum atom, a gallium atom, an indium atom, tin Atom, lead atom, iron atom, cobalt atom, nickel atom, copper atom and silver atom are preferable, and lithium atom, sodium atom and magnesium atom are more preferable from the viewpoint of securing high electromotive force.

In the formula (II), six M are the same as the six M in the formula (I). In Formula (II), A is the same as A in Formula (I).

In the formula (II), p is a number from 0 to 4. Since p differs depending on the valence of X ¹ (the valence of the element), it is preferable that p is appropriately determined according to the valence of X ¹ . For example, when the valence of X ¹ is 1, p is preferably a number from 0 to 4. Further, when the valence of X ¹ is 2, p is preferably a number from 0 to 2. Further, when the valence of X ¹ is 3, p is preferably a number from 0 to 1.3.

Examples of the chevrel compound represented by the formula (II) include Mg ₂ Mo ₆ S ₈ , Mg ₂ Mo ₅ CrS ₈ , Mg ₂ Mo ₄ Cr ₂ S ₈ , Mg ₂ Mo ₃ Cr ₃ S ₈ , and Mg ₂ Mo. _{_{_{_{2 Cr 4 S 8, Mg 2}}}} MoCr 5 S 8, Mg 2 Cr 6 S 8, Mg 2 Mo 6 Se 8, Mg 2 Mo 5 CrSe 8, Mg 2 Mo 4 Cr 2 Se 8, Mg 2 Mo 3 Cr 3 Se ₈ , Mg ₂ Mo ₂ Cr ₄ Se ₈ , Mg ₂ MoCr ₅ Se ₈ , Mg ₂ Mo ₆ Te ₈ , Mg ₂ Mo ₅ CrTe ₈ , Mg ₂ Mo ₄ Cr ₂ Te ₈ , Mg ₂ Mo ₃ Cr ₃ Te ₈ , _{_{_{_{mg 2 Mo 2 Cr 4 Te 8}}}} , mg 2 MoCr 5 the like Te ₈ and the like, and the present invention is not limited only to those exemplified. Among the chevrel compounds, compounds containing a large amount of chromium atoms and / or sulfur atoms having a small atomic weight are preferable from the viewpoint of securing a higher mass energy density. Among the chevrel compounds, Mg ₂ Mo ₆ S ₈ , Mg ₂ Mo ₅ CrS ₈ , Mg ₂ Mo ₄ Cr ₂ S ₈ , Mg ₂ Mo ₃ Cr ₃ S ₈ , from the viewpoint of securing a higher mass energy density, Mg ₂ Mo ₂ Cr ₄ S ₈ , Mg ₂ MoCr ₅ S ₈ and Mg ₂ Cr ₆ S ₈ are more preferred.

The positive electrode may be an electrode made of a cluster compound having a cluster represented by formula (I), or an electrode in which a positive electrode material containing a positive electrode active material made of the cluster compound is supported on a current collector. Also good. When the positive electrode is an electrode in which the positive electrode material is supported on a current collector, the positive electrode is directly applied by, for example, applying the positive electrode material to the current collector, pulse laser deposition, sputtering, liquid phase synthesis, or the like. In particular, the positive electrode material can be deposited on the current collector.

The positive electrode material contains a positive electrode active material made of the cluster compound. Further, the positive electrode material may further contain a conductive additive and a binder as necessary.

Examples of the conductive aid include carbon powder, oxygen-deficient titanium oxide, and metal fine powder, but the present invention is not limited to such examples. Since the content rate of the conductive auxiliary agent in the positive electrode material varies depending on the type of conductive auxiliary agent and the like, it is preferable to determine appropriately according to the type of conductive auxiliary agent.

Examples of the binder include thermoplastic fluororesin bodies such as polyvinylidene fluoride and styrene-butadiene rubber, but the present invention is not limited to such examples. Since the content of the binder in the positive electrode material varies depending on the type of the binder and the like, it is preferable to appropriately determine the content according to the type of the binder and the like.

Examples of the material constituting the current collector include platinum, aluminum, palladium, copper, aluminum, nickel, niobium, molybdenum, stainless steel, and a carbon material. However, the present invention is limited to only such examples. It is not something. Since the material constituting the current collector varies depending on the type of secondary battery, the usage of the secondary battery, the type of the cluster compound, the type of the electrolyte, etc., the type of the secondary battery, the usage of the secondary battery, It is preferable to select appropriately according to the type of the cluster compound, the type of the electrolytic solution, and the like. Examples of the shape of the current collector include a porous body, a plate, and a roll-shaped thin plate. However, the present invention is not limited to such an example.

The negative electrode is an electrode including a negative electrode active material. Examples of the negative electrode active material include metals such as s-block metal and p-block metal; alloys containing the metal as a base metal; compounds of the metal; carbon materials; silicon or a compound thereof. However, the present invention is not limited to such examples. Examples of the s block metal include alkali metals such as lithium, sodium, and potassium; alkaline earth metals such as beryllium, magnesium, and calcium; however, the present invention is not limited to such examples. . Examples of the p-block metal include aluminum, gallium, germanium, indium, tin, lead, and the like, but the present invention is not limited to such examples. Examples of the alloy include Mg ₂ Sn, but the present invention is not limited to such examples. Examples of the metal compound include metal oxides such as titanium, but the present invention is not limited to such examples. Examples of the carbon material include acetylene black, graphite, and glassy carbon. However, the present invention is not limited to such examples. Examples of the silicon include amorphous silicon, but the present invention is not limited to such examples. Examples of the silicon compound include silicon dioxide and magnesium silicide (Mg ₂ Si), but the present invention is not limited to such examples. Since the negative electrode active material varies depending on the type of secondary battery, the usage of the secondary battery, the type of the cluster compound, the type of the electrolyte, etc., the type of the secondary battery, the usage of the secondary battery, It is preferable to select appropriately according to the type and the type of the electrolytic solution. For example, when the energy density is required to be 200 Wh / kg or more, among the negative electrode active materials, from the viewpoint of securing a higher mass energy density, magnesium simple substance, tin simple substance and silicon simple substance are preferable, and magnesium simple substance is preferable. More preferred.

The negative electrode may be an electrode made of the negative electrode active material, or an electrode in which a negative electrode material containing the negative electrode active material is supported on a current collector. When the negative electrode is an electrode in which the negative electrode material is supported on a current collector, the negative electrode can be produced, for example, by applying the negative electrode material to a current collector. The negative electrode material contains the negative electrode active material. The negative electrode material may further contain a conductive auxiliary and a binder as necessary. The conductive assistant and binder in the negative electrode material are the same as the conductive assistant and binder in the positive electrode material.

The electrolyte solution varies depending on the mode of suppression of penetration of the liquid into the voids of the atomic arrangement structure of the cluster compound, the type of the secondary battery, the use of the secondary battery, the type of the cluster compound, etc. It is preferable to determine appropriately according to the mode of suppressing the penetration of the liquid into the voids of the atomic arrangement structure of the cluster compound, the type of the secondary battery, the use of the secondary battery, the type of the cluster compound, and the like.

In the secondary battery according to the present embodiment, the intrusion of the liquid into the gap is, for example,
(A) A liquid having a chemical property that is difficult to enter the voids of the atomic arrangement structure of the cluster compound as a liquid capable of transferring carrier ions between the positive electrode and the negative electrode (hereinafter also referred to as “liquid A”). Using
(B) As a liquid capable of transferring carrier ions between the positive electrode and the negative electrode, a liquid made of a compound having a bulkiness sufficient to prevent the cluster compound from entering the voids of the atomic arrangement structure (hereinafter referred to as “liquid”) , Also referred to as “liquid B”),
(C) It is suppressed by covering the surface of the positive electrode active material of the positive electrode with a coating material that allows carrier ions to pass but does not allow the liquid to pass.

The liquid A is a liquid having a chemical property that hardly penetrates into the voids of the atomic arrangement structure of the cluster compound. Examples of the liquid A include an ionic liquid and a mixture obtained by mixing at least two kinds of the ionic liquids, but the present invention is not limited to such examples. Examples of the ionic liquid include an ionic liquid containing an anion having a halogen atom and an organic cation or a metal cation. However, the present invention is not limited to such examples. Among the liquids A, an ionic liquid containing an organic cation, an anion having a halogen atom, and an organic cation or a metal cation is used from the viewpoint of more efficiently performing a charge / discharge reaction in the negative electrode and ensuring a higher electromotive force. preferable. As the ionic liquid, for example, an ionic liquid containing at least two types of anions and at least two types of organic cations; an ionic liquid containing at least two types of anions and at least two types of metal cations; Examples of the ionic liquid include both types of anions and both an organic cation and a metal cation. However, the present invention is not limited to such examples.

The anion is an anion having a halogen atom. Examples of the anion having a halogen atom include a non-coordinating halide anion, a metal halogen complex anion, and the formula (III):

(Wherein R ³ represents a halogen atom or an alkyl group having 1 to 8 carbon atoms having the halogen atom)
The sulfonate anion etc. which are represented by these are mentioned, However, This invention is not limited only to this illustration. These anions have a halogen atom and can constitute an ionic liquid capable of securing a sufficient mass energy density together with a cation described later.

Examples of the non-coordinating halide anion include, for example, a hydrogen halide anion [for example, the formula (VI):

(Wherein X ³ represents a halogen atom, and r represents a number of 1 to 4)
A hydrogen halide anion (for example, HF ₂ ⁻ , H ₂ F ₃ ⁻ , H ₃ F ₄ ⁻ etc.)], a hexafluorophosphate anion (PF ₆ ⁻ ), a tetrafluoroborate anion (BF ₄ ⁻ ), etc. Although mentioned, this invention is not limited only to this illustration. In the formula (VI), X ³ is a halogen atom. In the formula (VI), r is a number from 1 to 4. The halogen atom in formula (VI) is the same as the halogen atom in formula (III). Among the non-coordinating halide anions, a hydrogen halide anion and a tetrafluoroborate anion (BF ₄ ⁻ ) are preferable, and a hydrogen halide anion is more preferable from the viewpoint of securing a higher mass energy density.

Examples of the metal halide complex anion include hexafluoroarsenate anion (AsF ₆ ⁻ ), hexafluoroniobate anion (NbF ₆ ⁻ ), hexafluoro tantalate anion (TaF ₆ ⁻ ), heptafluorotungstateate anion (WF). ₇ ^-), hexafluoro back anion (UF ₆ ^-), tetrafluoro oxovanadium anions (VOF ₄ ^-), pentafluorophenyl oxo molybdenum anions (MoOF ₅ ^-) but the like, the present invention is only to those exemplified It is not limited. Among the metal halide complex anions, from the viewpoint of securing a sufficient mass energy density, a tetrafluorooxovanadium anion (VOF ₄ ⁻ ) and a hexafluoroarsenate anion (AsF ₆ ⁻ ) are preferable, and the tetrafluorooxovanadium anion ( VOF ₄ ⁻ ) is more preferable.

In the formula (III), X ² represents a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. However, the present invention is not limited to such examples. Among the halogen atoms, a fluorine atom and a chlorine atom are preferable, and a chlorine atom is more preferable from the viewpoint of reducing the weight and ensuring the corrosion resistance. In the formula (III), q is a number from 1 to 2. Examples of the halogenoaluminate anion represented by the formula (III) include a tetrachloroaluminate anion (AlCl ₄ ⁻ ) and a heptachlorodialuminate anion (Al ₂ Cl ₇ ⁻ ). It is not limited only to such illustration. Among the halogenoaluminate anions represented by the formula (III), AlCl ₄ ⁻ and Al ₂ Cl ₇ ⁻ are preferable.

In the formula (IV), R ¹ and R ² are each independently a halogen atom or an alkyl group having 1 to 8 carbon atoms having the halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, but the present invention is not limited only to such illustration. Among the halogen atoms, a fluorine atom is preferable from the viewpoint of securing a higher mass energy density. The number of carbon atoms in the alkyl group having 1 to 8 carbon atoms having a halogen atom ensures hydrophobicity and sufficient thermal stability suitable for suppressing the penetration of the solvent into the voids of the atomic arrangement structure of the cluster compound. From the viewpoint, it is 1 or more, and from the viewpoint of ensuring the viscosity of the electrolyte suitable for obtaining a high electromotive force, it is 8 or less, preferably 2 or less. Examples of the alkyl group having 1 to 8 carbon atoms having a halogen atom include a perfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluoropentyl group, a perfluoroheptyl group, and a perfluorohexyl group. Perfluoroalkyl group having 1 to 8 carbon atoms such as perfluorooctyl group, perchloromethyl group, perchloroethyl group, perchloropropyl group, perchlorobutyl group, perchloropentyl group, perchloroheptyl group, Perchloroalkyl groups having 1 to 8 carbon atoms such as chlorohexyl group and perchlorooctyl group; perbromomethyl group, perbromoethyl group, perbromopropyl group, perbromobutyl group, perbromopentyl group, perbromoheptyl group , Perbromohexyl group, perbromooctyl A perbromoalkyl group having 1 to 8 carbon atoms, such as periodomethyl group, periodoethyl group, periodiopropyl group, periodiobutyl group, periodiopentyl group, periodioheptyl group, periodiohexyl group, periodiod Examples thereof include a C 1-8 alkyl group such as an octyl group, but the present invention is not limited to such examples. Among these alkyl groups having 1 to 8 carbon atoms having a halogen atom, perfluoroalkyl groups having 1 to 8 carbon atoms are preferable from the viewpoint of ensuring the viscosity of an electrolyte suitable for obtaining a high electromotive force. A perfluoroalkyl group having 1 to 4 carbon atoms is more preferred, and a perfluoromethyl group is more preferred. Examples of the sulfonylamide anion represented by the formula (IV) include bis (halogenosulfonyl) amide anion such as bis (fluorosulfonyl) amide anion; bis (halogenoalkylsulfonyl) amide such as bis (trifluoromethylsulfonyl) amide anion Although an anion etc. are mentioned, this invention is not limited only to this illustration.

In the formula (V), R ³ is a C 1-8 alkyl group having a halogen atom. The number of carbon atoms of the alkyl group in the formula (V) is 1 to 8, preferably 1 to 6, and more preferably 1 to 4 in order to ensure the viscosity of the electrolytic solution suitable for obtaining a high electromotive force. The alkyl group having 1 to 8 carbon atoms having a halogen atom in the formula (V) is the same as the alkyl group having 1 to 8 carbon atoms having a halogen atom in the formula (IV). Examples of the sulfonate anion represented by the formula (V) include halogenoalkyl sulfonate anions such as a trifluoromethyl sulfonate anion and a pentafluoroethyl sulfonate anion, but the present invention is limited only to such examples. Is not to be done.

Among the anions, the viscosity of the electrolyte suitable for obtaining a high electromotive force, the hydrophobicity suitable for suppressing the penetration of the solvent into the voids of the atomic arrangement structure of the cluster compound, and sufficient chemical stability From the viewpoint of securing the sulfonylamide anion represented by formula (IV) and the sulfonate anion represented by formula (V), bis (halogenosulfonyl) amide anion, bis (halogenoalkylsulfonyl) amide anion and halogenoalkylsulfo A narate anion is more preferable, and a bis (fluorosulfonyl) amide anion, a bis (trifluoromethylsulfonyl) amide anion, and a trifluoromethylsulfonate anion are more preferable.

The cation is a metal cation or an organic cation. These cations have a halogen atom and can form an ionic liquid capable of securing a sufficient mass energy density together with the anion.

Examples of the metal cation include an alkali metal cation and an alkaline earth metal cation, but the present invention is not limited to such examples. Examples of the alkali metal cation include a lithium cation, a sodium cation, a potassium cation, and a cesium cation, but the present invention is not limited to such examples. Examples of the alkaline earth metal cation include beryllium cation, magnesium cation, and calcium cation, but the present invention is not limited to such examples. Among the metal cations, lithium cation, sodium cation, magnesium cation and cesium cation are preferable when a rocking chair type storage battery is constructed.

Examples of the organic cation include formula (VII):

(Wherein R ¹⁰ and R ¹¹ each independently represents an alkyl group having 1 to 8 carbon atoms)
An imidazolium cation represented by the formula (X):

(Wherein R ¹² represents an alkyl group having 1 to 8 carbon atoms)
Although the pyridinium cation represented by these is mentioned, this invention is not limited only to this illustration.

In the formula (VII), R ⁴ , R ⁵ , R ⁶ and R ⁷ are each independently an optionally substituted alkyl group having 1 to 8 carbon atoms or alkyloxyalkyl having 1 to 8 carbon atoms. It is a group. The number of carbon atoms of the alkyl group which may have a substituent in the formula (VII) is 1 to 8, preferably 1 to 6, from the viewpoint of securing the viscosity of the electrolyte suitable for obtaining a high electromotive force. More preferably, it is 1 to 4. Examples of the alkyl group having 1 to 8 carbon atoms in the alkyl group which may have a substituent include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, and a pentyl group. A straight or branched alkyl group having 1 to 8 carbon atoms such as hexyl group, heptyl group and octyl group; carbon such as cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group and cyclooctyl group Examples thereof include alicyclic alkyl groups of 1 to 8, but the present invention is not limited to such examples. Examples of the substituent include a hydroxyl group, a carbonyl group, a phenyl group, a benzyl group, a nitric acid group (—NO ₃ group), a sulfuric acid group, and a sulfone group, but the present invention is limited only to such examples. is not. The carbon number of the alkyloxyalkyl group in formula (VII) is 1 to 8, preferably 1 to 6, and more preferably 1 to 4 from the viewpoint of improving the heat resistance of the electrolyte. Examples of the alkyloxyalkyl group having 1 to 8 carbon atoms include methoxymethyl group, 2-methoxyethyl group, ethoxymethyl group, 2-ethoxyethyl group, 2- (n-propoxy) ethyl group, 2- (n- Examples include isopropoxy) ethyl group, 2- (n-butoxy) ethyl group, 2-isobutoxyethyl group, 2- (tert-butoxy) ethyl group, 1-ethyl-2-methoxyethyl group and the like. Is not limited to such examples.

Examples of the quaternary ammonium cation represented by the formula (VII) include N, N, N-trimethyl-N-propylammonium cation, N, N, N-trimethyl-N-hexylammonium cation, N, N, N— Examples include trimethyl-N- (2-hydroxymethyl) ammonium cation and N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium cation, but the present invention is limited to such examples only. It is not a thing. Among the quaternary ammonium cations represented by the formula (VII), N, N, N-trimethyl-N— is used from the viewpoint of securing sufficient conductivity and viscosity of an electrolyte suitable for obtaining a high electromotive force. Propyl ammonium cation, N, N, N-trimethyl-N-hexyl ammonium cation, N, N, N-trimethyl-N- (2-hydroxymethyl) ammonium cation and N, N-diethyl-N-methyl-N- ( 2-Methoxyethyl) ammonium cation is preferred.

In the formula (VIII), R ⁸ and R ⁹ are each independently an alkyl group having 1 to 8 carbon atoms. The number of carbon atoms of the alkyl group in the formula (VIII) is 1 to 8, preferably 1 to 6, more preferably 1 from the viewpoint of securing sufficient conductivity and viscosity of the electrolyte suitable for obtaining a high electromotive force. ~ 4. The alkyl group having 1 to 8 carbon atoms in the formula (VIII) is the same as the alkyl group having 1 to 8 carbon atoms in the formula (VII). In Formula (VIII), A is a direct bond or a methylene group.

In formula (VIII), the cation in which Y is a direct bond is represented by formula (VIIIa):

(Wherein R ⁸ and R ⁹ are the same as above)
It is a pyrrolidinium cation represented by Examples of the pyrrolidinium cation represented by the formula (VIIIa) include N, N-dimethylpyrrolidinium cation, N-methyl-N-ethylpyrrolidinium cation, N-methyl-N-propylpyrrolidinium cation, N-methyl-N-butylpyrrolidinium cation, N-methyl-N-pentylpyrrolidinium cation, N-methyl-N-hexylpyrrolidinium cation, N-methyl-N-octylpyrrolidinium cation, N- Examples include ethyl-N-butylpyrrolidinium cation, but the present invention is not limited to such examples.

In the formula (VIII), the cation where Y is a methylene group is the formula (VIIIb):

(Wherein R ⁸ and R ⁹ are the same as above)
A piperidinium cation represented by: Examples of the piperidinium cation represented by the formula (VIIIb) include N, N-dimethylpiperidinium cation, N-methyl-N-ethylpiperidinium cation, N-methyl-N-propylpiperidinium cation, N-methyl-N-butylpiperidinium cation, N-methyl-N-pentylpiperidinium cation, N-methyl-N-hexylpiperidinium cation, N-methyl-N-octylpiperidinium cation, N- Examples include ethyl-N-propylpiperidinium cation, but the present invention is not limited to such examples.

In the formula (IX), R ¹⁰ and R ¹¹ each independently represents an alkyl group having 1 to 8 carbon atoms. The number of carbon atoms of the alkyl group in the formula (IX) is 1 to 8, preferably 1 to 6, more preferably 1 from the viewpoint of ensuring sufficient conductivity and viscosity of the electrolyte suitable for obtaining a high electromotive force. ~ 4. The alkyl group having 1 to 8 carbon atoms in the formula (IX) is the same as the alkyl group having 1 to 8 carbon atoms in the formula (VII). Examples of the imidazolium cation represented by the formula (IX) include 1,3-dimethylimidazolium cation, 1-methyl-3-ethylimidazolium cation, 1-methyl-3-propylimidazolium cation, 1-methyl- 3-butylimidazolium cation, 1-methyl-3-pentylimidazolium cation, 1-methyl-3-hexylimidazolium cation, 1-methyl-3-heptylimidazolium cation, 1-methyl-3-octylimidazolium cation 1,3-diethylimidazolium cation, 1-ethyl-3-propylimidazolium cation, 1-ethyl-3-butylimidazolium cation, etc., but the present invention is not limited to such examples. Absent.

In the formula (X), R ¹² is an alkyl group having 1 to 8 carbon atoms. The number of carbon atoms of the alkyl group in the formula (X) is 1 to 8, preferably 1 to 6, more preferably 1 from the viewpoint of securing sufficient conductivity and viscosity of the electrolyte suitable for obtaining a high electromotive force. ~ 4. The alkyl group having 1 to 8 carbon atoms in the formula (X) is the same as the alkyl group having 1 to 8 carbon atoms in the formula (VII). Examples of the pyridinium cation represented by the formula (X) include N-methylpyridinium cation, N-ethylpyridinium cation, N-propylpyridinium cation, N-butylpyridinium cation, N-pentylpyridinium cation, N-hexylpyridinium cation, Examples include N-heptylpyridinium cation and N-octylpyridinium cation, but the present invention is not limited to such examples.

Among the cations, an alkali metal cation, an alkaline earth metal cation, a quaternary ammonium cation represented by the formula (VII) and a cation represented by the formula (VIII) are preferable, and a lithium cation, a sodium cation, a cesium cation, and a magnesium cation. N-trimethyl-N-propylammonium cation, N-trimethyl-N-hexylammonium cation, N, N, N-trimethyl-N- (2-hydroxymethyl) ammonium cation, N, N-diethyl-N-methyl- N- (2-methoxyethyl) ammonium cation, N-methyl-N-propylpyrrolidinium cation and N-methyl-N-propylpiperidinium cation are more preferred.

Since the combination of anion and cation differs depending on the type of secondary battery, the use of the secondary battery, the type of the cluster compound, etc., the type of secondary battery, the use of the secondary battery, the type of the cluster compound, etc. It is preferable to determine appropriately.

The liquid B is a liquid made of a compound having a sufficient bulk to prevent the cluster compound from entering the voids of the atomic arrangement structure. In the present specification, “bulky enough to prevent entry into the gap” means a bulkiness larger than the size of the inlet portion of the gap.

Examples of the liquid B include glycol ether compounds such as a glyme compound, but the present invention is not limited to such examples. In the present specification, the “glyme compound” refers to a symmetric glycol ether in which hydroxyl groups at both ends of alkyl glycol are substituted with the same substituent. Here, examples of the substituent include an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, a propyl group, and a butyl group, but the present invention is not limited only to such examples. .

Examples of the glycol ether compound include monoglyme (ethylene glycol dimethyl ether), ethyl monoglyme (ethylene glycol diethyl ether), butyl monoglyme (ethylene glycol dibutyl ether), methyl diglyme (diethylene glycol dimethyl ether), ethyl diglyme (diethylene glycol diethyl). Ether), butyl diglyme (diethylene glycol dibutyl ether), methyl triglyme (triethylene glycol dimethyl ether), ethyl triglyme (triethylene glycol diethyl ether), butyl triglyme (triethylene glycol diethyl ether), methyl tetraglyme (tetraethylene) Glycol dimethyl ether), ethyl tetraglyme (Te La ethylene glycol diethyl ether), although glyme compound, such as butyl tetraglyme (tetraethylene glycol dibutyl ether) and the like, and the present invention is not limited only to those exemplified.

Among the liquids B, the viewpoint of ensuring the viscosity of the electrolyte solution that is sufficiently bulky to prevent the cluster compound from entering the voids of the atomic arrangement structure and that is suitable for obtaining a high electromotive force. From the above, the glyme compound is preferred, and methyltetraglyme is more preferred.

The covering material is a compound that allows carrier ions to pass but does not allow the liquid to pass. Examples of the covering material include vinylidene glycol and magnesium oxide, but the present invention is not limited to such examples. The positive electrode active material can be coated with the coating material by, for example, a sputtering method. Since the amount of the coating material used for coating the positive electrode active material varies depending on the type of the coating material, the type of the positive electrode active material, the amount of the positive electrode active material, etc., the type of the coating material, the type of the positive electrode active material, and the positive electrode active material It is preferable to determine appropriately according to the amount of the amount.

As described above, the secondary battery according to the present embodiment has a high electromotive force. Therefore, the secondary battery according to the present embodiment is developed with an energy supply and demand system capable of optimizing energy supply and demand, with development of a hybrid vehicle and an electric vehicle with higher fuel efficiency, more downsized and higher performance. This is useful for developing mobile devices.

Next, the present invention will be described in more detail based on examples. However, the present invention is not limited to such examples.

Experimental example 1
While oxygen bubbling, copper Chevrel compound (Cu ₂ Mo ₆ S ₈₎ to remove the copper ions from a compound having a Mo ₆ S ₈ clusters (hereinafter referred to as "Mo ₆ S ₈ cluster compounds") to obtain a powder . Impurities for confirming the position were mixed into the obtained powder of the Mo ₆ S ₈ cluster compound to obtain a sample A. In addition, the Mo ₆ S ₈ cluster compound powder was immersed in tetrahydrofuran to obtain a Mo ₆ S ₈ cluster compound-containing tetrahydrofuran. Impurities for confirming the position were mixed in the resulting Mo ₆ S ₈ cluster compound-containing tetrahydrofuran to obtain Sample B. X-ray diffraction of Sample A and Sample B was examined using an X-ray diffractometer [manufactured by Rigaku Corporation, trade name: SMART LAB].

FIG. 1 shows the results of examining the X-ray diffraction of Mo ₆ S ₈ cluster compound powder (sample A) and Mo ₆ S ₈ cluster compound-containing tetrahydrofuran (sample B) in Experimental Example 1. In FIG. 1, (A) is an X-ray diffraction pattern of Mo ₆ S ₈ cluster compound powder (sample A), (B) is an X-ray diffraction pattern of Mo ₆ S ₈ cluster compound-containing tetrahydrofuran (sample B), (C ) Is the X-ray diffraction pattern of Cu ₂ Mo ₆ S _{8 in} the Inorganic Crystal Structure Database (hereinafter referred to as “ICSD”), and (D) is the X-ray diffraction pattern of the Mo ₆ S ₈ cluster compound of ICSD. Show. The dotted line indicates the position of the impurity peak for position confirmation.

From the results shown in Figure 1, the position of the peak of the impurity in the X-ray diffraction pattern of the position and the Mo ₆ S ₈ cluster compounds containing tetrahydrofuran peak of an impurity in the X-ray diffraction pattern of the powder of Mo ₆ S ₈ cluster compound identical (See peaks P1 to P7 in the figure). However, a peak derived from the Mo ₆ S ₈ cluster compound in the X-ray diffraction pattern of the Mo ₆ S ₈ cluster compounds containing tetrahydrofuran, derived from Mo ₆ S ₈ cluster compound in the X-ray diffraction pattern of the powder of Mo ₆ S ₈ cluster compounds It can be seen that the peak is different from the peak. These results show that the structure of the powder and Mo ₆ S ₈ cluster compounds containing the structure of tetrahydrofuran Mo ₆ S ₈ cluster compounds are different from each other. Therefore, from these results, the structure of a cluster compound having a cluster represented by the formula (I), for example, a chevrel compound such as a Mo ₆ S ₈ cluster compound is changed by the penetration of the solvent into the structure of the cluster compound. It is suggested to do.

Experimental example 2
An impurity for confirming the position was mixed in the powder of the copper chevrel compound to obtain a sample A. Moreover, the copper chevrel compound was immersed in tetrahydrofuran to obtain a copper chevrel compound-containing tetrahydrofuran. Impurities for confirming the position were mixed in the obtained copper chevrel compound-containing tetrahydrofuran to obtain Sample B. X-ray diffraction of Sample A and Sample B was examined using an X-ray diffractometer [manufactured by Rigaku Corporation, trade name: SMART LAB].

FIG. 2 shows the results of examining the X-ray diffraction of the copper chevrel compound powder (sample A) and the copper chevrel compound-containing tetrahydrofuran (sample B) in Experimental Example 2. In FIG. 2, (A) is an X-ray diffraction pattern of a copper chevrel compound powder (sample A), (B) is an X-ray diffraction pattern of a copper chevrel compound (sample B), and (C) is an ICSD copper chevrel compound. An X-ray diffraction pattern is shown. The dotted line indicates the position of the impurity peak for position confirmation, and the solid line indicates the peak derived from the copper chevrel compound.

The results shown in FIG. 2 show that the position of the impurity peak in the X-ray diffraction pattern of the copper chevrel compound powder and the position of the impurity peak in the X-ray diffraction pattern of the copper chevrel compound-containing tetrahydrofuran are the same ( (See peaks P1 and P2 in the figure). However, the peak derived from the copper chevrel compound in the X-ray diffraction pattern of the powder of the copper chevrel compound (eg, see peaks A1 to A8 in the figure) is derived from the copper chevrel compound in the X-ray diffraction pattern of the copper chevrel compound-containing tetrahydrofuran. It can be seen that the peak is shifted to the left from the peak (for example, see peaks B1 to B8 in the figure). From these results, it is suggested that the lattice constant of the copper chevrel compound is increased in the presence of tetrahydrofuran as a solvent. Therefore, these results suggest that the structure of the copper chevrel compound, which is a cluster compound having a cluster represented by the formula (I), changes as the solvent enters the structure.

Example 1
(1) Production of three-electrode cell body A three-electrode cell body 10a shown in Fig. 3 was constructed in a glove box maintained in an argon gas atmosphere. The constructed three-electrode cell body 10a includes a container 11, a working electrode 13 having a Mo ₆ S ₈ cluster compound as an active material, a counter electrode 14 made of a magnesium sheet, and a reference electrode 15. A hole portion 11b for providing the counter electrode 14 and a hole portion 11c for providing the reference electrode 15 are formed on the upper surface portion of the container 11, and a hole portion for providing the working electrode 13 on the bottom portion. 11a is formed. An electrolytic solution 16 is accommodated in the container 11. The working electrode 13 is an electrode coated on the surface of an aluminum sheet so that the Mo ₆ S ₈ cluster compound is 1 to 10 mg / cm ² . In the working electrode 13, the Mo ₆ S ₈ cluster compound serves as an active material for ion insertion and desorption during the oxidation-reduction reaction. The reference electrode 15 is formed integrally with a reference electrode main body 15a made of a magnesium rod, a glass tube portion 15b that isolates the reference electrode main body 15a from the electrolyte solution 16, and the glass tube portion 15b. It consists of a porous glass portion 15c for ensuring electrical connection between the inside and the outside of 15b, and a reference electrode electrolyte 15d accommodated in the glass tube portion 15b. Therefore, the reference electrode main body 15 a is electrically connected to the working electrode 13 and the counter electrode 14, but is configured not to directly contact the electrolyte solution 16.

(2) Preparation of electrolyte solution N-methyl-N-propylpiperidinium-bis (trifluoromethanesulfonyl) imide (hereinafter referred to as “PP13-TFSI”) and magnesium bis (trifluoromethylsulfonyl) imide (hereinafter referred to as “Mg”) (TFSI) ₂ ”) was mixed so that PP13-TFSI / Mg (TFSI) ₂ (molar ratio) was 6.7 / 1 to obtain an electrolytic solution.

(3) Production of three-electrode cell The electrolytic solution obtained in (2) above was placed in the container 11 of the three-electrode cell body 10a obtained in (1) to obtain a three-electrode cell 10.

Test example 1
Cyclic voltammetry was performed at a scanning speed of 0.5 mV / s using the three-electrode cell obtained in Example 1 and an electrochemical measuring device (trade name: SP-300, manufactured by BioLogic). I did it.

In Test Example 1, a working electrode in the case of using an electrolytic solution containing PP13-TFSI and Mg (TFSI) ₂ , a working electrode having a Mo ₆ S ₈ cluster compound as an active material, and a counter electrode made of a magnesium sheet The result of investigating the relationship between the terminal potential and the current is shown in FIG.

From the results shown in FIG. 4, an electrolytic solution containing PP13-TFSI and Mg (TFSI) ₂ , a working electrode having a Mo ₆ S ₈ cluster compound as an active material, and a counter electrode made of a magnesium sheet were used. In this case, it can be seen that a peak potential is observed in the vicinity of 3V. Note that PP13-TFSI is presumed to have an electrochemical property that hardly penetrates into the voids of the atomic arrangement structure of the cluster compound. Therefore, from these results, using an electrolyte containing an ionic liquid that has an electrochemical property that does not easily penetrate into the voids of the atomic arrangement structure of the cluster compound, the liquid can penetrate into the voids of the atomic arrangement structure of the cluster compound. By suppressing, it is suggested that a high electromotive force can be secured.

Test example 2
Using the three-electrode cell obtained in Example 1 and an electrochemical measurement apparatus (trade name: SP-300, manufactured by BioLogic), the working electrode 13 and the counter electrode 14 in the three-electrode cell Chronopotentiometry was carried out by applying a current of 0.02 mA for 120 minutes (discharging only 1/20 of the maximum capacity). The active material of the working electrode after discharge was collected and analyzed by X-ray diffraction. As a control, the powder of the Mo ₆ S ₈ cluster compound obtained in Experimental Example 1 was analyzed by X-ray diffraction.

In Test Example 2, the result of examining the X-ray diffraction of the active material of the working electrode after discharge is shown in FIG. In the figure, (A) is an X-ray diffraction pattern of the Mo ₆ S ₈ cluster compound obtained in Experimental Example 1, (B) is an X-ray diffraction pattern of the active material of the working electrode after discharge, and (C) is an inorganic crystal. Platinum data in a structural database (hereinafter referred to as “ICSD”), (D) is aluminum data in ICSD, (E) is Mg ₂ Mo ₆ S ₈ data in ICSD, and (F) is MgMo ₆ S _{8 in} ICSD. (G) shows data of Mo ₆ S ₈ in ICSD, (H) shows data of Cu ₂ Mo ₆ S ₈ in ICSD, and (I) shows data of Cu ₂ Mo ₆ S _{8 in} ICSD.

From the results shown in FIG. 5, it can be seen that in the X-ray diffraction pattern of the active material of the working electrode after discharge, the height of the peak a2 is approximately the same as the height of the peak b2. In contrast, in the X-ray diffraction pattern of the Mo ₆ S ₈ cluster compound obtained in Experimental Example 1, it can be seen that the peak a1 is higher than the peak b1. Moreover, in the X-ray diffraction pattern of the active material of the working electrode after discharge, a peak c2 was observed, but in the X-ray diffraction pattern of the Mo ₆ S ₈ cluster compound obtained in Experimental Example 1, the peak c2 It can be seen that no peak is observed at the position corresponding to (see c1). In the data of Mg ₂ Mo ₆ S ₈ in ICSD, a peak is seen at the position corresponding to the peak c2, but in the data of Mo ₆ S _{8 in} ICSD, a peak is seen at the position corresponding to the peak c2. Absent. Therefore, these results suggest that the active material of the working electrode after discharge contains magnesium atoms.

Example 2
(1) Preparation of Electrolytic Solution N-methyl-N-propylpyrrolidinium-bis (trifluoromethanesulfonyl) imide (hereinafter referred to as “P13-TFSI”) and Mg (TFSI) ₂ are combined with P13-TFSI / Mg ( TFSI) ₂ (molar ratio) was mixed to be 6.7 / 1 to obtain an electrolytic solution.

(2) Production of Beaker Cell A beaker cell 20 shown in FIG. 6 was constructed in a glove box maintained in an argon gas atmosphere. The constructed beaker cell 20 includes a container 21, a positive electrode 22 having a Mo ₆ S ₈ cluster compound as an active material, and a mixture of magnesium tin and tin (hereinafter referred to as “Mg ₂ Sn / Sn”) as an active material. The anode 23 is composed of a reference electrode 24 made of polished metal magnesium, and an electrolytic solution 25. The positive electrode 22 is an electrode coated on the surface of an aluminum sheet so that the Mo ₆ S ₈ cluster compound is 1 to 10 mg / cm ² . The negative electrode 23 is an electrode coated on the surface of a platinum sheet so that Mg ₂ Sn / Sn is 1 to 10 mg / cm ² .

Test example 3
Using the beaker cell obtained in Example 2 and an electrochemical measurement apparatus (trade name: SP-300, manufactured by BioLogic), the cut-off potential was set to 0.5 V, and the charge / discharge characteristics were examined. It was.

In Test Example 3, the results of examining the time-dependent changes in the terminal potential and current of the working electrode are shown in FIG. 7A, and the results of examining the time-dependent change in the electric capacity of the beaker cell are shown in FIG. 7B. In FIG. 7, (a) shows the terminal potential of the working electrode, and (b) shows the current.

From the result shown in FIG. 7, it can be seen that the initial potential is about 2.5V. Such an initial potential is that of a conventional magnesium secondary battery (Non-patent Document 1) including a positive electrode containing a chevrel compound as a positive electrode active material, and an electrolytic solution made of a solution obtained by dissolving a Grignard reagent and aluminum chloride in tetrahydrofuran. The value is about twice as high as the initial potential. Note that P13-TFSI, like PP13-TFSI, is presumed to have an electrochemical property that hardly penetrates into the voids of the atomic arrangement structure of the cluster compound. Therefore, from these results, using an electrolyte containing an ionic liquid that has an electrochemical property that does not easily penetrate into the voids of the atomic arrangement structure of the cluster compound, the liquid can penetrate into the voids of the atomic arrangement structure of the cluster compound. By suppressing, it is suggested that a high electromotive force can be secured.

Test example 4
The charge / discharge reaction was performed using the beaker cell obtained in Example 2 and an electrochemical measurement apparatus (trade name: SP-300, manufactured by BioLogic). Next, the positive electrode active material present in the positive electrode after discharge was collected and analyzed by X-ray diffraction. As a control, the powder of the Mo ₆ S ₈ cluster compound obtained in Experimental Example 1 was analyzed by X-ray diffraction.

In addition, the amount of the element in the location where the positive electrode active material exists in the positive electrode after discharge (see the circled portion (A region) in FIG. 8A) and the location where the positive electrode active material does not exist in the positive electrode after discharge (conducting aid). The amount of the element in the location where the agent and the binder are present (see the encircled portion (B region) in FIG. 8B) is measured with a scanning electron microscope-energy dispersive X-ray analysis method (acceleration voltage: 15. 0 kV and irradiation current: 4.4 nA), and the ratio (composition ratio) of each element at the location where the positive electrode active material was present to the amount of each element where the positive electrode active material was absent in the positive electrode after discharge was examined.

In Test Example 4, the results of examining the X-ray diffraction of the positive electrode active material present in the positive electrode after discharge are shown in FIG. 9, (A) is an X-ray diffraction pattern of the Mo ₆ S ₈ cluster compound obtained in Experimental Example 1, (B) is an X-ray diffraction pattern of the positive electrode active material present in the positive electrode after discharge, and (C). Is the data of platinum in ICSD, (D) is the data of aluminum in ICSD, (E) is the data of Mg ₂ Mo ₆ S ₈ in ICSD, (F) is the data of MgMo ₆ S ₈ in ICSD, (G) is the ICSD data, of Cu ₂ Mo ₆ S ₈ data Mo ₆ S _8, in (H) is ICSD in (I) shows the data of the Cu ₂ Mo ₆ S ₈ in ICSD. Moreover, in Test Example 4, the result of examining the ratio (composition ratio) of each element at the location where the positive electrode active material is present to the amount of each element where the positive electrode active material is absent in the positive electrode after discharge is shown in FIG.

From the results shown in FIG. 9, it can be seen that the peak a2 is lower than the peak b2 in the X-ray diffraction pattern of the positive electrode active material of the positive electrode after discharge. In contrast, it can be seen that the peak a1 in the X-ray diffraction pattern of the Mo ₆ S ₈ cluster compound obtained in Experimental Example 1 is higher than the peak b1. Moreover, in the X-ray diffraction pattern of the positive electrode active material of the positive electrode after discharge, a peak c2 was observed, but in the X-ray diffraction pattern of the Mo ₆ S ₈ cluster compound obtained in Experimental Example 1, the peak c2 It can be seen that no peak is observed at the position corresponding to (see c1). In the data of Mg ₂ Mo ₆ S ₈ in ICSD, a peak is observed at the position corresponding to the peak c2, but in the data of Mo ₆ S _{8 in} ICSD, a peak is present in the position corresponding to the peak c2. can not see. Therefore, these results suggest that the positive electrode active material of the positive electrode after discharge contains magnesium atoms.

Further, from the results shown in FIG. 10, the ratio (composition ratio) of each element in the location where the positive electrode active material is present to the amount of each element in the location where the positive electrode active material is not present in the positive electrode after discharge exceeds 1. (Composition ratio: 5.0645) suggests that the positive electrode active material contains magnesium atoms.

Test Example 5
Using the beaker cell obtained in Example 2 and an electrochemical measurement apparatus (trade name: SP-300, manufactured by BioLogic), cyclic voltammetry was performed at a scanning speed of 1 mV / s.

In Test Example 5, an electrolytic solution containing P13-TFSI and Mg (TFSI) ₂ , a positive electrode having a Mo ₆ S ₈ cluster compound as an active material, and a negative electrode having Mg ₂ Sn / Sn as an active material were used. A cyclic voltammogram in this case is shown in FIG. In the figure, (A) shows the relationship between the terminal potential of the positive electrode and the current, and (B) shows the relationship between the terminal potential of the positive electrode and the terminal potential of the negative electrode.

From the results shown in FIG. 11, it can be seen that two peaks (a1 and a2) are observed near the oxidation-reduction potential in the positive electrode. Therefore, from these results, an electrolytic solution containing P13-TFSI and Mg (TFSI) ₂ , a positive electrode having a Mo ₆ S ₈ cluster compound as an active material, and a negative electrode having Mg ₂ Sn / Sn as an active material are obtained. It can be seen that when used, a redox reaction can be performed.

Test Example 6
The charge / discharge characteristics were examined using the beaker cell obtained in Example 2 and an electrochemical measurement apparatus (trade name: SP-300, manufactured by BioLogic).

In Test Example 6, an electrolytic solution containing P13-TFSI and Mg (TFSI) ₂ , a positive electrode having a Mo ₆ S ₈ cluster compound as an active material, and a negative electrode having Mg ₂ Sn / Sn as an active material were used. FIG. 12 shows the result of examining the charge / discharge characteristics in this case. In the figure, (A) shows the change over time in the potential difference (Ewe-Ece) between the positive electrode and the negative electrode, (B) shows the change over time in the current, (C) shows the change over time in the terminal potential of the negative electrode, (D ) Indicates the change with time of the terminal potential of the positive electrode.

From the results shown in FIG. 12, it can be seen that the positive electrode is well charged and discharged and a high electromotive force of about 3 V is obtained (see arrow a1 in the figure). In the negative electrode, although magnesium electrodeposition is observed (see arrow a2 in the figure), it can be seen that the magnesium tends to passivate. From these results, an electrolytic solution containing P13-TFSI and Mg (TFSI) ₂ , a positive electrode having a Mo ₆ S ₈ cluster compound as an active material, and a negative electrode having Mg ₂ Sn / Sn as an active material were used. In this case, it can be seen that a high electromotive force can be obtained in the charge / discharge reaction despite the formation of passive magnesium.

Example 3
Working electrode made of aluminum sheet coated with 1 to 10 mg / cm ^{2 of} Cu ₂ Mo ₆ S ₈ cluster compound in a glove box maintained in an argon gas atmosphere, and reference electrode made of lithium rod A three-electrode cell comprising a counter electrode made of a magnesium sheet and an electrolyte was constructed. Note that the electrolytic solution includes cesium-bis (trifluoromethanesulfonyl) imide (hereinafter referred to as “Cs-TFSI”), lithium-bis (trifluoromethanesulfonyl) imide (hereinafter referred to as “Li-TFSI”), and Mg (TFSI). ₂ is an electrolytic solution obtained by mixing Cs-TFSI / Li-TFSI / Mg (TFSI) ₂ (volume ratio) to 8/1/1.

Test Example 7
Using the three-electrode cell obtained in Example 3 and an electrochemical measuring device (trade name: SP-300, manufactured by BioLogic), the temperature of the electrolyte: 180 ° C. and the scanning speed: 5 mV / Cyclic voltammetry was performed under the conditions of s.

In Test Example 7, an electrolytic solution containing Cs-TFSI, Li-TFSI, and Mg (TFSI) ₂ , a working electrode having Cu ₂ Mo ₆ S ₈ as an active material, and a counter electrode made of a magnesium sheet were used. FIG. 13 shows the result of examining the relationship between the terminal potential of the working electrode and the current when cyclic voltammetry was performed at 180 ° C.

From the results shown in FIG. 13, an electrolyte containing Cs-TFSI, Li-TFSI and Mg (TFSI) ₂ , a working electrode having Cu ₂ Mo ₆ S ₈ as an active material, and a counter electrode made of a magnesium sheet Is used at 180 ° C., copper is desorbed from Cu ₂ Mo ₆ S ₈ , and the result of scanning electron microscope / energy dispersive X-ray composition analysis shows that copper is completely removed. Therefore, it can be seen that the desorption of copper occurs at about 3.7V. Note that Cs-TFSI, like PP13-TFSI and P13-TFSI, is presumed to have an electrochemical property that hardly penetrates into the voids of the atomic arrangement structure of the cluster compound. Therefore, from these results, using an electrolyte containing an ionic liquid that has an electrochemical property that does not easily penetrate into the voids of the atomic arrangement structure of the cluster compound, the liquid can penetrate into the voids of the atomic arrangement structure of the cluster compound. By suppressing, it is suggested that the charge / discharge reaction can be performed at a high potential.

Example 4
Working electrode made of a platinum sheet coated with a Cu ₂ Mo ₆ S ₈ cluster compound in an amount of 1 to 10 mg / cm ² in a glove box kept in an argon gas atmosphere, and a reference electrode made of a lithium rod And a three-electrode cell comprising a counter electrode made of a lithium sheet and an electrolyte. Note that the electrolyte was mixed with Cs-TFSI, Li-TFSI, and Mg (TFSI) ₂ so that Cs-TFSI / Li-TFSI / Mg (TFSI) ₂ (volume ratio) was 8/1/1. It is the electrolyte solution obtained by doing.

Test Example 8
Using the three-electrode cell obtained in Example 4 and an electrochemical measurement apparatus (trade name: SP-300, manufactured by BioLogic), the temperature of the electrolyte: 150 ° C. and the scanning speed: 5 mV / Cyclic voltammetry was performed under the conditions of s.

In Test Example 8, an electrolytic solution containing Cs-TFSI, Li-TFSI, and Mg (TFSI) ₂ , a working electrode having Cu ₂ Mo ₆ S ₈ as an active material, and a counter electrode made of a lithium sheet were used. FIG. 14 shows the result of examining the relationship between the terminal potential of the working electrode and the current when cyclic voltammetry was performed at 150 ° C.

From the results shown in FIG. 14, an electrolyte containing Cs-TFSI, Li-TFSI, and Mg (TFSI) ₂ , a working electrode having Cu ₂ Mo ₆ S ₈ as an active material, and a counter electrode made of a lithium sheet Is used at 150 ° C., copper is desorbed from the Mo ₆ S ₈ cluster compound, and copper is completely removed from the results of scanning electron microscope and energy dispersive X-ray composition analysis. As can be seen, it can be seen that the desorption of copper occurs at about 3.7V. As described above, Cs-TFSI is presumed to have an electrochemical property that hardly penetrates into the voids of the atomic arrangement structure of the cluster compound. Therefore, from these results, using an electrolyte containing an ionic liquid that has an electrochemical property that does not easily penetrate into the voids of the atomic arrangement structure of the cluster compound, the liquid can penetrate into the voids of the atomic arrangement structure of the cluster compound. By suppressing, it is suggested that the charge / discharge reaction can be performed at a high potential.

Example 5
In a glove box maintained in an argon gas atmosphere, a working electrode made of a platinum sheet coated with a Mo ₆ S ₈ cluster compound of 1 to 10 mg / cm ² , a reference electrode made of a lithium rod, A three-electrode cell having a counter electrode made of a lithium sheet and an electrolyte was constructed. Note that the electrolyte was mixed with Cs-TFSI, Li-TFSI, and Mg (TFSI) ₂ so that Cs-TFSI / Li-TFSI / Mg (TFSI) ₂ (volume ratio) was 8/1/1. It is the electrolyte solution obtained by doing.

Test Example 9
Using the three-electrode cell obtained in Example 5 and an electrochemical measurement apparatus (trade name: SP-300, manufactured by BioLogic), the temperature of the electrolyte: 150 ° C. and the scanning speed: 5 mV / Cyclic voltammetry was performed under the conditions of s.

In Test Example 8, using an electrolytic solution containing Cs-TFSI, Li-TFSI, and Mg (TFSI) ₂ , a working electrode having a Mo ₆ S ₈ cluster compound as an active material, and a counter electrode made of a lithium sheet, FIG. 15 shows the results of examining the relationship between the terminal potential of the working electrode and the current when cyclic voltammetry was performed at 150 ° C.

From the results shown in FIG. 15, an electrolyte solution containing Cs-TFSI, Li-TFSI, and Mg (TFSI) ₂ , a working electrode having a Mo ₆ S ₈ cluster compound as an active material, and a counter electrode made of a lithium sheet Is used at 150 ° C., copper is desorbed from the Mo ₆ S ₈ cluster compound, and copper is completely removed by the results of scanning electron microscope and energy dispersive X-ray composition analysis. It can be seen that copper desorption occurs at about 3.7V. As described above, Cs-TFSI is presumed to have an electrochemical property that hardly penetrates into the voids of the atomic arrangement structure of the cluster compound. Therefore, from these results, using an electrolyte containing an ionic liquid that has an electrochemical property that does not easily penetrate into the voids of the atomic arrangement structure of the cluster compound, the liquid can penetrate into the voids of the atomic arrangement structure of the cluster compound. By suppressing, it is suggested that the charge / discharge reaction can be performed at a high potential.

Example 6
(1) Preparation of electrolyte solution Cs-TFSI, Li-TFSI, and Mg (TFSI) ₂ are adjusted so that Cs-TFSI / Li-TFSI / Mg (TFSI) ₂ (volume ratio) is 8/1/1. Mixing was performed to obtain an electrolytic solution.

(2) Production of Beaker Cell A beaker cell 30 shown in FIG. 16 was constructed in a glove box maintained in an argon gas atmosphere. The constructed beaker cell 30 includes a container 31, a positive electrode 32 having a Mo ₆ S ₈ cluster compound as an active material, a negative electrode 33 having Mg ₂ Sn / Sn as an active material, and a reference electrode 33 made of polished metallic lithium. And an electrolytic solution 35. The positive electrode 32 is made of a positive electrode material containing a Mo ₆ S ₈ cluster compound, a conductive auxiliary agent, and a binder (composition: Mo ₆ S ₈ cluster compound / conductive auxiliary agent / binder (volume ratio) = 8: 1: 1) is an electrode applied on the surface of an aluminum sheet so that it is 1 to 10 mg / cm ² . The negative electrode 33 is an electrode coated on the surface of a platinum sheet so that the negative electrode material made of Mg ₂ Sn / Sn is 1 to 10 mg / cm ² .

Test Example 10
The charge / discharge characteristics were examined using the beaker cell obtained in Example 6 and an electrochemical measurement apparatus (trade name: SP-300, manufactured by BioLogic).

In Test Example 10, an electrolytic solution containing Cs-TFSI, Li-TFSI, and Mg (TFSI) ₂ , a positive electrode having a Mo ₆ S ₈ cluster compound as an active material, and a negative electrode having Mg ₂ Sn / Sn as an active material FIG. 17 shows the result of investigating the charge / discharge characteristics when using. In the figure, (A) shows the change over time in the potential difference (Ewe-Ece) between the positive electrode and the negative electrode, (B) shows the change over time in the current, (C) shows the change over time in the terminal potential of the negative electrode, (D ) Shows the terminal potential change with time of the positive electrode. Further, in Test Example 10, the results of examining the time-dependent changes in the terminal potential and current of the working electrode are shown in FIG. 18A, and the results of examining the time-dependent change in the electric capacity of the beaker cell are shown in FIG. 18B. Show. In FIG. 18, (a) shows the change over time in the potential difference (Ewe-Ece) between the positive electrode and the negative electrode, (b) shows the change over time in the terminal potential of the positive electrode, and (c) shows the change over time in the terminal potential of the negative electrode. , (D) shows changes in current over time.

From the results shown in FIG. 17, an electrolytic solution containing Cs-TFSI, Li-TFSI, and Mg (TFSI) ₂ , a positive electrode having a Mo ₆ S ₈ cluster compound as an active material, and Mg ₂ Sn / Sn active. It can be seen that a high electromotive force of about 3 V is obtained at the positive electrode by using the negative electrode as the substance (see the enclosed part a1 in the figure). On the other hand, in the negative electrode, although the electrodeposition of magnesium is observed, it can be seen that the magnesium tends to passivate (see the enclosed part a2 in the figure). Further, from the results shown in FIG. 18, an electrolytic solution containing Cs-TFSI, Li-TFSI, and Mg (TFSI) ₂ , a positive electrode having a Mo ₆ S ₈ cluster compound as an active material, and Mg ₂ Sn / Sn It can be seen that a discharge capacity of about 20 mAh / g can be obtained by using a negative electrode having an active material. As described above, Cs-TFSI is presumed to have an electrochemical property that hardly penetrates into the voids of the atomic arrangement structure of the cluster compound. Therefore, from these results, using an electrolyte containing an ionic liquid that has an electrochemical property that does not easily penetrate into the voids of the atomic arrangement structure of the cluster compound, the liquid can penetrate into the voids of the atomic arrangement structure of the cluster compound. It is suggested that a high discharge capacity can be secured by the suppression.

Test Example 11
The charge / discharge reaction was carried out using the beaker cell obtained in Example 6 and an electrochemical measurement apparatus (trade name: SP-300, manufactured by BioLogic). The positive electrode active material of the positive electrode after charge and the positive electrode after discharge was collected and analyzed by X-ray diffraction. As a control, powders of Cu ₂ Mo ₆ S ₈ , LiMo ₆ S ₈ , Li ₃ Mo ₆ S ₈ and Li ₄ Mo ₆ S ₈ were analyzed by X-ray diffraction method.

Further, the amount of the element in the location where the positive electrode active material exists in the positive electrode after discharge (see the circled portion (A region) in FIG. 19A) and the location where the positive electrode active material does not exist in each positive electrode after discharge (conductivity) The amount of the element in the presence of the auxiliary agent and the binder (see the circled portion (B region) in FIG. 19 (b)) was determined by scanning electron microscope-energy dispersive X-ray analysis (acceleration voltage: 15 0.0 kV and irradiation current: 4.4 nA), and the ratio (composition ratio) of each element in the location where the positive electrode active material is present to the amount of each element in the location where the positive electrode active material is absent in the positive electrode after discharge was examined. .

20 and 21 show the results of examining the X-ray diffraction of the positive electrode active material of each of the positive electrode after charging and the positive electrode after discharging in Test Example 11. 20, (A) is an X-ray diffraction pattern of Cu ₂ Mo ₆ S ₈ , (B) is an X-ray diffraction pattern of a positive electrode active material of a positive electrode after charging, and (C) is a positive electrode active material of a positive electrode after discharging. (D) is platinum data in ICSD, (E) is aluminum data in ICSD, (F) is Mg ₂ Mo ₆ S ₈ data in ICSD, and (G) is MgMo ₆ S in ICSD. ₈ data, (H) shows Mo ₆ S ₈ data in ICSD, (I) shows Cu ₂ Mo ₆ S ₈ data in ICSD, and (J) shows Cu ₂ Mo ₆ S ₈ data in ICSD. In FIG. 21, (A) is an X-ray diffraction pattern of Cu ₂ Mo ₆ S ₈ , (B) is an X-ray diffraction pattern of a positive electrode active material of the positive electrode after charging, and (C) is a positive electrode of the positive electrode after discharging. X-ray diffraction pattern of active material, (D) X-ray diffraction pattern of LiMo ₆ S ₈ , (E) X-ray diffraction pattern of Li ₃ Mo ₆ S ₈ , (F) X of Li ₄ Mo ₆ S ₈ Line diffraction pattern, (G) is platinum data in ICSD, (H) is aluminum data in ICSD, (I) is Mg ₂ Mo ₆ S ₈ data in ICSD, and (J) is MgMo ₆ S ₈ data in ICSD. Data, (K) shows Mo ₆ S ₈ data in ICSD, (L) shows Cu ₂ Mo ₆ S ₈ data in ICSD, and (M) shows Cu ₂ Mo ₆ S ₈ data in ICSD. Moreover, in Test Example 11, the result of examining the ratio (composition ratio) of each element in the location where the positive electrode active material is present to the amount of each element in the location where the positive electrode active material is not present in the positive electrode after discharge is shown in FIG.

From the results shown in FIG. 20, in the X-ray diffraction pattern of the positive electrode active material of the positive electrode after charging, the peak a2 is from the position of the peak a1, which is the corresponding peak in the X-ray diffraction pattern of Cu ₂ Mo ₆ S _8. You can see that it has shifted to the left. Further, in the X-ray diffraction pattern of the positive electrode active material of the positive electrode after charging, the peak b2 is shifted to the left from the position of the peak b1, which is the corresponding peak in the X-ray diffraction pattern of Cu ₂ Mo ₆ S ₈ . I understand. On the other hand, from the results shown in FIG. 20, in the X-ray diffraction pattern of the positive electrode active material of the positive electrode after discharge, the peak a3 is the corresponding peak in the X-ray diffraction pattern of Cu ₂ Mo ₆ S ₈ . It can be seen that it can be seen at almost the same position. In addition, in the X-ray diffraction pattern of the positive electrode active material of the positive electrode after discharge, the peak b3 is found at substantially the same position as the peak b1, which is the corresponding peak in the X-ray diffraction pattern of Cu ₂ Mo ₆ S _8. I understand. Therefore, these results suggest that magnesium is inserted into and desorbed from the positive electrode active material constituting the positive electrode during the charge / discharge reaction.

Further, from the results shown in FIG. 21, in the X-ray diffraction pattern of the positive electrode active material of the positive electrode after charging, the peak a1 is the position of the peak a2 in the X-ray diffraction pattern of LiMo ₆ S ₈ and Li ₃ Mo ₆ S it can be seen that seen in a position different from the position of the peak a4 in the X-ray diffraction pattern of the position and Li ₄ Mo ₆ S ₈ peak a3 in the X-ray diffraction pattern of _8. Furthermore, in the X-ray diffraction pattern of the positive electrode active material of the positive electrode after charging, the peak b1 is the position of the peak b2 in the X-ray diffraction pattern of LiMo ₆ S _{8 and} the peak b3 in the X-ray diffraction pattern of Li ₃ Mo ₆ S _8. It can be seen that this is seen at a position different from the position of the peak b4 in the X-ray diffraction pattern of Li ₄ Mo ₆ S ₈ . Therefore, it can be seen from these results that lithium is not inserted into the positive electrode active material constituting the positive electrode in the charge / discharge reaction.

Further, from the results shown in FIG. 22, the ratio (composition ratio) of each element in the location where the positive electrode active material is present to the amount of each element in the location where the positive electrode active material is not present in the positive electrode after discharge exceeds 1. (Composition ratio: 4.0769). Therefore, these results suggest that the positive electrode active material contains magnesium atoms.

Example 7
A working electrode made of an aluminum sheet coated with a Mo ₆ S ₈ cluster compound in an amount of 1 to 10 mg / cm ² in a glove box kept in an argon gas atmosphere, a reference electrode made of a magnesium rod, A three-electrode cell comprising a counter electrode made of a magnesium sheet and an electrolyte was constructed. The electrolytic solution is Mg (TFSI) ₂ , PP13-TFSI, and P13-TFSI, and Mg (TFSI) ₂ / PP13-TFSI / P13-TFSI (volume ratio) is 0.3 / 1/1. It is the electrolyte solution obtained by mixing.

Example 8
A working electrode made of an aluminum sheet coated with a Mo ₆ S ₈ cluster compound in an amount of 1 to 10 mg / cm ² in a glove box kept in an argon gas atmosphere, a reference electrode made of a magnesium rod, A three-electrode cell comprising a counter electrode made of a magnesium sheet and an electrolyte was constructed. The electrolytic solution is an electrolytic solution obtained by mixing Mg (TFSI) ₂ and PP13-TFSI so that Mg (TFSI) ₂ / PP13-TFSI (molar ratio) is 1 / 6.7. is there.

Test Example 12
Using the three-electrode cell obtained in Example 7 or Example 8 and an electrochemical measurement device (trade name: SP-300, manufactured by BioLogic), the temperature of the electrolyte: 25 ° C. and scanning Speed: Cyclic voltammetry was performed at 20 mV / s.

In Test Example 12, the results of examining the relationship between the potential and the current density when using the three-electrode cell obtained in Example 7 and Example 8 are shown in FIG. In the figure, the solid line shows the relationship between the potential and current density when the three-electrode cell obtained in Example 7 is used, and the broken line shows the potential and current when the three-electrode cell obtained in Example 8 is used. The relationship with density is shown.

From the results shown in FIG. 23, the electrodeposition current [see (A1)] when the three-electrode cell obtained in Example 7 was used was the same as that of the eight-electrode cell obtained in Example 8. It can be seen that it is larger than the electrodeposition current in the case [see (A2)]. Further, the anode current [see (B1)] when using the three-electrode cell obtained in Example 7 is larger than the anode current when using the three-electrode cell obtained in Example 8. It can be seen [see (B2)]. Furthermore, when the three-electrode cell obtained in Example 7 is used, the decomposition of the electrolytic solution tends to be further suppressed as compared with the case where the three-electrode cell obtained in Example 8 is used. You can see [see (C)]. From these results, at least two kinds of ionic liquids having different cations are mixed, and in addition to carrier ions (magnesium cations), two kinds of cations (N-methyl-N-propylpiperidinium cation and til-N— By using propylpyrrolidinium cation), it is suggested that the formation of passive magnesium can be suppressed and the charge / discharge reaction can be performed more efficiently.

From the above results, in the secondary battery, as the positive electrode, an electrode including the cluster compound having the cluster represented by the formula (I), and the electrolyte is an electrochemical solution that does not easily enter the voids of the atomic arrangement structure of the cluster compound. It is suggested that a high electromotive force can be ensured by using an electrolyte containing a liquid having a property and capable of transferring carrier ions between the positive electrode and the negative electrode.

Example 9
A working electrode composed of an aluminum sheet coated with 1 to 10 mg / cm ² of Mo ₆ S ₈ cluster compound in a glove box maintained in an argon gas atmosphere, a reference electrode composed of a magnesium rod, magnesium A three-electrode cell comprising a counter electrode made of a sheet made of sheet and an electrolyte was constructed. The electrolytic solution is an electrolytic solution composed of a 0.5 M Mg (TFSI) ₂ methyltriglyme solution.

Test Example 13
Using the three-electrode cell obtained in Example 9 and an electrochemical measurement apparatus (trade name: SP-300, manufactured by BioLogic), the temperature of the electrolyte: 25 ° C. and the scanning speed: 5 mV / Cyclic voltammetry was performed under the conditions of s.

In Test Example 13, a cyclic voltammogram when using the three-electrode cell obtained in Example 9 is shown in FIG. In the figure, (A) shows the relationship between the potential and the current, and (B) shows the relationship between the potential and the terminal potential of the counter electrode. FIG. 25 shows the result of converting the relationship between the potential and current shown in FIG. 24 to the Mg ²⁺ / Mg standard.

From the results shown in FIG. 24 and FIG. 25, it can be confirmed that the insertion / extraction of magnesium ions occurs at about 3 V vs. the magnesium pole reference electrode. It is suggested that the charge / discharge reaction can be carried out satisfactorily by using an electrolytic solution containing a liquid (for example, methyltriglyme, etc.) made of a compound having a bulkiness sufficient to prevent penetration into The In addition, it is estimated that methyltriglyme is sufficiently bulky to suppress the penetration of the atomic arrangement structure of the cluster compound into the voids. Therefore, from these results, as an electrolytic solution, a liquid (for example, methyl diglyme, methyl triglyme, It is suggested that the charge / discharge reaction can be carried out satisfactorily by using an electrolytic solution containing methyltetraglyme and the like.

Experimental example 3
In a glove box maintained in an argon gas atmosphere, a working electrode made of an aluminum sheet coated with a copper chevrel compound at 1 to 10 mg / cm ² , a reference electrode made of metallic lithium, and made of metallic lithium A three-electrode cell having a counter electrode and an electrolytic solution [a mixture of ethylene carbonate and dimethyl carbonate containing 1M lithium hexafluorophosphate (volume ratio of ethylene carbonate / dimethyl carbonate = 1/2)] was constructed.

Experimental Example 4
In a glove box maintained in an argon gas atmosphere, a working electrode made of an aluminum sheet coated with a copper chevrel compound at 1 to 10 mg / cm ² , a reference electrode made of metallic lithium, and made of metallic lithium Three electrodes provided with a counter electrode and an electrolytic solution [a mixture of ethylene carbonate and dimethyl carbonate containing 1M lithium hexafluorophosphate and 3% by mass vinylene carbonate (ethylene carbonate / dimethyl carbonate (volume ratio) = 1/2)] A formula cell was constructed. In addition, vinylene carbonate forms a film on the surface of the copper chevrel compound constituting the positive electrode active material of the positive electrode, thereby suppressing the intrusion of the liquid component of the electrolyte into the voids of the atomic arrangement structure of the copper chevrel compound. Is.

Test Example 14
Using the three-electrode cell obtained in Experimental Example 3 or Experimental Example 4 and an electrochemical measuring device (trade name: SP-300, manufactured by BioLogic), the scanning speed was 0.5 mV / s. Click voltammetry measurement was performed.

In Test Example 14, the results of examining the relationship between the terminal potential of the working electrode and the current when the three-electrode cell obtained in Experimental Example 3 was used are shown in FIG. 26 and the three-electrode cell obtained in Experimental Example 14 FIG. 27 shows the result of investigating the relationship between the terminal potential of the working electrode and the current when using. In FIG. 26, (A1) is a peak indicating elimination of lithium cations from the A site of the copper chevrel compound, (A2) is a peak indicating insertion of lithium cations into the A site of the copper chevrel compound, and (B1) is copper. A peak indicating elimination of a lithium cation from the B site of the chevrel compound, (B2) is a peak indicating insertion of a lithium cation into the B site of the copper chevrel compound, and (C1) is a copper cation from the A site of the copper chevrel compound. (B2) is a peak indicating insertion of a copper cation into the B site of the copper chevrel compound.

From the results shown in FIG. 26, when an electrolytic solution not containing vinylene carbonate was used (Experimental Example 3), a peak indicating lithium cation desorption and insertion at the A site of the copper chevrel compound [(A1) in the figure] And (A2)] and a peak (see (B1) and (B2) in the figure) indicating the desorption and insertion of the lithium cation at the B site of the copper chevrel compound. However, the peak indicating the detachment of the copper cation from the A site of the copper chevrel compound (see (C1) in the figure) and the peak indicating the detachment of the copper cation from the B site of the copper chevrel compound (in the figure, ( D1)] can be seen, but it can be seen that no peaks indicating the insertion of copper cations at the A and B sites of the copper chevrel compound are observed.

On the other hand, from the results shown in FIG. 27, when an electrolytic solution containing vinylene carbonate was used (Experimental Example 4), peaks indicating lithium cation desorption and insertion at the B site of the copper chevrel compound [(B1 ) And (B2)]. However, it can be seen that both a peak indicating the desorption and insertion of the copper cation at the A site of the copper chevrel compound and a peak indicating the desorption and insertion of the copper cation at the B site of the copper chevrel compound are observed. In addition, when compared with the results shown in FIG. 26, a reduction current due to insertion of lithium ions is observed from around 3.7 V and 3.3 V, and therefore a reduction product film is formed by the addition of vinylene carbonate. I understand. Furthermore, although not shown, when the three-electrode cell obtained in Experimental Example 3 is used, a peak indicating the detachment and insertion of a lithium cation at the A site of the copper chevrel compound and the lithium at the B site of the copper chevrel compound Peaks indicating cation desorption and insertion were observed.

In addition, when vinylene carbonate forms a film on the surface of the copper chevrel compound that constitutes the positive electrode active material of the positive electrode, the penetration of the liquid component of the electrolytic solution into the voids of the atomic arrangement structure of the copper chevrel compound is suppressed. Conceivable. Therefore, from these results, in the secondary battery, a high electromotive force was obtained by using, as the positive electrode, an electrode containing a cluster compound having a cluster represented by the formula (I) and having the surface of the cluster compound coated. It is suggested that can be secured.

As described above, in a secondary battery, as a positive electrode, an electrode including a cluster compound having a cluster represented by the formula (I), and as an electrolyte, a liquid capable of transferring carrier ions between the positive electrode and the negative electrode And by suppressing the intrusion of the liquid into the voids of the atomic arrangement structure of the cluster compound, a high electromotive force can be ensured. Therefore, a secondary battery for storing power, a hybrid vehicle, It is suggested that it is suitable as an in-vehicle secondary battery used for automobiles, a secondary battery for mobile devices, and the like.

DESCRIPTION OF SYMBOLS 10 Three electrode type cell 10a Three electrode type cell main body 11 Container

11b Hole part

11c Hole part

11a Hole part 13 Working electrode 14 Counter electrode 15 Reference electrode 15a Reference electrode main body 15b Glass tube part 15c Porous glass part 15d Electrolyte for reference electrode 16 Electrolytic solution 20 Beaker cell 21 Container 22 Positive electrode 23 Negative electrode 24 Reference electrode 25 Electrolytic solution 30 Beaker cell 31 Container 32 Positive electrode 33 Negative electrode 33 Reference electrode 35 Electrolytic solution

Claims

A negative electrode, a positive electrode, and an electrolyte solution interposed between the positive electrode and the negative electrode,
The positive electrode has the formula (I):

(In the formula, 6 M's are each independently a chromium atom, a molybdenum atom or a tungsten atom, and A's are each independently a chalcogen atom)
An electrode including a cluster compound having a cluster represented by:
The electrolyte contains a liquid capable of transferring carrier ions between the positive electrode and the negative electrode;
A secondary battery, wherein the liquid is prevented from entering the voids of the atomic arrangement structure of the cluster compound.
The secondary battery according to claim 1, wherein the liquid is an ionic liquid or a mixture obtained by mixing at least two kinds of the ionic liquids.
The secondary battery according to claim 2, wherein the ionic liquid is an ionic liquid containing an anion having a halogen atom and an organic cation or a metal cation.
The ionic liquid may be used as an anion as a non-coordinating halide anion, a metal halide complex anion, and

(Wherein X 2 represents a halogen atom and q represents a number of 1 to 2)
A halogenoamate anion represented by formula (IV):

(Wherein R 1 and R 2 each independently represents a halogen atom or a C 1-8 alkyl group having a halogen atom)
A sulfonylamide anion represented by formula (V):

(Wherein R 3 represents a halogen atom or an alkyl group having 1 to 8 carbon atoms having the halogen atom)
And an anion selected from the group consisting of sulfonate anions represented by formula (VII):

(Wherein R 4 , R 5 , R 6 and R 7 each independently represents an optionally substituted alkyl group having 1 to 8 carbon atoms or an alkyloxyalkyl group having 1 to 8 carbon atoms) )
A quaternary ammonium cation represented by formula (VIII):

(Wherein R 8 and R 9 are each independently an alkyl group having 1 to 8 carbon atoms, Y represents a direct bond or a methylene group)
A cation represented by formula (IX):

(Wherein R 10 and R 11 each independently represents an alkyl group having 1 to 8 carbon atoms)
And an imidazolium cation represented by the formula (X):

(Wherein R 12 represents an alkyl group having 1 to 8 carbon atoms)
The secondary battery according to claim 3, which is an ionic liquid containing a cation selected from the group consisting of pyridinium cations represented by:
2. The secondary battery according to claim 1, wherein the liquid is a compound having a bulkiness sufficient to prevent entry of the atomic arrangement structure of the cluster compound into the voids.
The secondary battery according to claim 5, wherein the compound is a glycol ether compound.
The secondary battery according to any one of claims 1 to 6, wherein the cluster compound is a chevrel compound.
The chevrel compound has the formula (II):

(In the formula, each p 1 is independently an alkali metal atom, an alkaline earth metal atom, a group 12 typical metal atom, a group 13 typical metal atom, a group 14 typical metal atom, a 3d transition metal atom, or a 4d transition metal. Atoms, 6 M are the same as above, A is the same as above, p is a number from 0 to 4)
The secondary battery according to claim 7, which is a chevrel compound having a composition represented by: