JP2011142049A - Electrode, magnesium ion secondary battery, and power system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode which has strong oxidation force and is excellent in cycle characteristics, a magnesium ion secondary battery using the electrode, and a power system made of the magnesium ion secondary battery. <P>SOLUTION: The electrode for a magnesium ion secondary battery includes WO<SB>3</SB>, and is a cathode 1. It is preferable that the cathode 1 includes a conductive assistant 22 arranged in the vicinity of particles of WO<SB>3</SB>powder 21, and a binder 23 for joining particles of the WO<SB>3</SB>powder 21 and particles of the conductive assistant 22 as well as the WO<SB>3</SB>powder 21. It is preferable that a ratio of the conductive assistant 22 to the whole cathode 1 is 1 or more and 40 or less mass%, and it is preferable that a ratio of the binder 23 to the whole cathode 1 is 1 or more and 40 or less mass%. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electrode, a magnesium ion secondary battery, and an electric power system, and more specifically, an electrode for a magnesium ion secondary battery, a magnesium ion secondary battery using the electrode, and the magnesium ion secondary battery. The present invention relates to an electric power system using.

  In recent years, attempts have been made to realize a low-carbon society as environmental measures such as global warming countermeasures. Specifically, the need for secondary batteries that can be charged and discharged is increasing toward the practical application of new energy such as solar power and wind power generation instead of energy using conventional oil or coal. . As the secondary battery, it is considered preferable to use a nonaqueous electrolytic solution. This is because a battery using a non-aqueous electrolyte can obtain a high voltage exceeding the electrolysis voltage of water and can obtain high energy.

  Currently, lithium ion batteries, which are mainly used as power sources for portable electronic devices, are rapidly spreading as secondary batteries, and entry into electric vehicles and power storage devices is also planned in the future. This is because the lithium ion battery has a high energy density, a long life, and the best performance. However, lithium has a small Clarke number indicating the amount of resources (ratio of elements present near the earth's surface). In other words, lithium is scarcely present as a mineral resource, and has the problem of resource depletion and high cost. For this reason, it is difficult to apply lithium ion batteries to devices such as electric vehicles that are larger than portable electronic devices. Therefore, development of a battery (magnesium ion battery) using magnesium, which is abundant in resources and cheaper than lithium, is in progress. Attempts have been made to use magnesium ion batteries for backup power sources for mobile phone base stations. For example, Japanese Patent Publication No. 2005-505099 (Patent Document 1) discloses an electrochemical battery in which the metal anode is magnesium.

Japanese Patent Publication No. 2005-505099

The electrochemical cell disclosed in Patent Document 1 includes a metal anode, an intercalation cathode, and a solid gel-like nonaqueous electrolyte. In the electrochemical cell, the anode is magnesium as described above, but the cathode is a chevrel phase intercalation cathode represented by Cu _x Mg _y Mo ₆ S ₈ (0 <x ≦ 1 and 0 <y ≦ 2). It is.

For example, in a battery other than an electrochemical battery for the backup power source described above, an active material containing sulfur such as Mo ₆ S ₈ (molybdenum sulfide) called a chevrel phase is used for a cathode (positive electrode) of a magnesium battery. Yes. However, the battery has a problem that it has a large irreversible capacity and poor cycle characteristics. This is because the positive electrode of the magnesium battery does not contain oxygen atoms but instead contains sulfur atoms. Since the oxygen atom is not contained and the sulfur atom is contained, the positive electrode has weak oxidizing power. For this reason, it is difficult to increase the voltage of the battery.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an electrode for forming a battery having high oxidizing power and good cycle characteristics. Moreover, it is providing the electric power system which consists of a magnesium ion secondary battery using the said electrode, and the said magnesium ion secondary battery.

Electrode according to the present invention comprises a WO _3, an electrode for a magnesium ion secondary battery. As a result of intensive studies, the inventors of the present invention have found that it is preferable to use an electrode containing WO ₃ (tungsten oxide) as an electrode for a magnesium secondary battery. If an electrode containing WO ₃ is used as a positive electrode of a magnesium ion secondary battery, the positive electrode has an excellent oxidizing power due to oxygen atoms contained in WO ₃ . Therefore, the capacity of the battery using the electrode can be increased, and the voltage during charging / discharging of the battery can be further increased. In addition, the cycle characteristics of the battery can be improved.

It is preferable that the electrode further includes a conductive additive arranged around a plurality of WO ₃ particles constituting the electrode. Since the above-mentioned WO ₃ is a non-conductor, in order to use it for the electrode (positive electrode), a conductive auxiliary agent coexisting with WO ₃ makes the entire electrode conductive. Is preferred. Moreover, the electric potential of the whole electrode containing a conductive support agent can be made constant by including a conductive support agent in an electrode and making an electrode have electroconductivity.

In the electrode, it is preferable that a ratio of the conductive auxiliary to the entire electrode is 1% by mass or more and 40% by mass or less. When the proportion of the conductive auxiliary agent is less than 1% by mass, the contribution of the conductive auxiliary agent to improve the conductivity of the entire electrode becomes small. Further, if the proportion of the conductive assistant exceeds 40% by mass, the proportion of the WO ₃ is reduced by the amount of the conductive assistant occupying the entire electrode, and the battery capacity is reduced and the cycle characteristics are reduced. May deteriorate. For this reason, it is preferable that the ratio which the conductive support agent occupies with respect to the whole electrode is 1 to 40 mass%, and it is more preferable that it is 5 to 20 mass% especially in the range mentioned above.

It is more preferable that the electrode further includes a binder that joins the above-described WO ₃ particles and the conductive auxiliary particles. If the powder particles of WO ₃ constituting the electrode or the particles of the conductive additive are connected by a binder, the electrode can be formed as an aggregate of the powder particles integrated. In addition, the shape and strength of the formed electrode can be maintained as desired.

  A battery using the electrode has a member called a current collector that is used as a flow path for distributing electrons from the electrode to the terminal. The current collector is disposed so as to be in close contact with the electrode so that electrons flow from the electrode to the terminal. The binder also has a role as an adhesive that maintains the current collector in close contact with the electrode and suppresses the electrode from falling off the current collector.

In the electrode, the proportion of the binder to the entire electrode is preferably 1% by mass or more and 40% by mass or less. When the proportion of the binder is less than 1% by mass, the contribution of the binder to maintain the shape of the entire electrode or to maintain the adhesion between the current collector and the electrode becomes small. Further, if the proportion of the conductive auxiliary exceeds 40% by mass, the proportion of the WO ₃ occupies lower by the amount of the binder occupying the entire electrode, and the battery capacity becomes smaller and the cycle characteristics deteriorate. there's a possibility that. For this reason, it is preferable that the ratio which the conductive support agent accounts with respect to the whole electrode is 1 to 40 mass%, and it is more preferable that it is 1 to 10 mass% especially in the range mentioned above.

WO ₃ described above preferably has a layered rock salt structure in crystal structure. If the crystal structure is a layered rock-salt structure, the effects of WO ₃ of increasing the overall battery capacity and improving cycle characteristics can be made more prominent.

  The magnesium ion secondary battery using the electrode according to the present invention can increase the capacity of the entire battery as described above, or can make the effect of improving the cycle characteristics more remarkable. Specifically, the electric capacity of the magnesium ion secondary battery is preferably 10 Ah or more and 100 Ah or less. Considering the balance of the cost, safety and fuel consumption of the magnesium ion secondary battery, the appropriate value of the electric capacity of the magnesium ion secondary battery is 10 Ah or more and 100 Ah or less as described above. In addition, it is more preferable that it is 30 Ah or more and 70 Ah or less in the range of the electric capacity mentioned above.

  The power system including the magnesium ion secondary battery described above can supply stable electric characteristics over a long period of time because the capacity of the magnesium ion secondary battery is increased and the cycle characteristics are improved.

  According to the present invention, it is possible to provide an electrode for forming a battery having a high voltage and good cycle characteristics due to its strong oxidizing power. In addition, a high-performance magnesium ion secondary battery using the electrode and a power system including the magnesium ion secondary battery can be provided.

It is a schematic sectional drawing for demonstrating the general usage aspect of the electrode which concerns on this invention. It is the schematic which shows the aspect of the area | region where the positive electrode and current collector of FIG. 1 were adhere | attached. It is the schematic which shows the aspect in case a conductive support agent and a binder are included in the positive electrode of FIG. 1 is a schematic perspective view showing an aspect of a laminate of a positive electrode and a negative electrode for forming a secondary battery according to Embodiment 1. FIG. It is the schematic which shows the aspect which winds the laminated body of FIG. 1 is a schematic external view of a magnesium ion secondary battery according to Embodiment 1. FIG. It is a schematic sectional drawing in line segment VII-VII of FIG. 4 is a graph showing results of evaluating discharge and charge of a magnesium ion secondary battery according to Embodiment 1. 4 is a schematic external view of a magnesium ion secondary battery according to Embodiment 2. FIG. FIG. 10 shows one aspect of the schematic cross-sectional view taken along line XX in FIG. 9. FIG. 10 is a schematic cross-sectional view taken along line XX in FIG. 9 and shows a mode different from FIG. 10. FIG. 11 is a schematic cross-sectional view taken along line XX in FIG. 9 and shows a mode different from FIG. 11. 9 is a schematic cross-sectional view taken along line XX in FIG. It is the schematic which shows the electric power system with which the magnesium ion secondary battery which concerns on this invention is used. It is the schematic which shows the backup power supply of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

  First, a general usage mode of the electrode according to the present invention will be described. FIG. 1 is a schematic diagram for ease of explanation, and is different from that showing the positional relationship of each member constituting an actual battery.

  The battery using the electrode according to the present invention is, for example, a magnesium ion secondary battery. As shown in FIG. 1, the magnesium ion secondary battery includes a positive electrode 1 and a negative electrode 2 as electrodes regardless of a specific mode. A separator 3 is disposed between the positive electrode 1 and the negative electrode 2. Each of the positive electrode 1 and the negative electrode 2 is bonded so as to be in close contact with the current collector 4.

  The magnesium ion secondary battery can be used multiple times by repeating charging and discharging. The positive electrode 1 is an electrode on the side where current flows out to the circuit (load) side connected to the magnesium ion secondary battery during discharging. The negative electrode 2 is an electrode on the side where current flows from the circuit (load) side connected to the magnesium ion secondary battery during discharging.

  Hereinafter, at the time of discharging, current flows out from the positive electrode 1, and thus electrons as a current source flow into the positive electrode 1. Further, since current flows into the negative electrode 2, electrons that are current sources flow out of the negative electrode 2. That is, a reduction reaction caused by electrons flowing in the positive electrode 1 and an oxidation reaction caused by electrons flowing in the negative electrode 2 occur.

  A separator 3 made of an insulating material is disposed between the positive electrode 1 and the negative electrode 2 in order to suppress the occurrence of a short circuit of current due to the contact between the positive electrode 1 and the negative electrode 2. In addition to preventing current short-circuiting, the separator 3 is used to hold, for example, an electrolyte injected into the battery in order to cause electrolysis of the battery in the battery container constituting the battery. There is also.

  The battery also has a terminal. The terminal is an area provided for outputting inflow and outflow of electrons due to a reduction reaction or an oxidation reaction occurring in the positive electrode 1 or the negative electrode 2 to an external circuit (load) in the form of current. In order to flow current (electrons) from the positive electrode 1 or the negative electrode 2 to the terminal, a current collector 4 serving as a flow path of current (electrons) from the positive electrode 1 and the negative electrode 2 to the terminal is disposed.

  The left current collector 4 in FIG. 1 is disposed in close contact with the positive electrode 1, and the right current collector 4 is in close contact with the negative electrode 2. For this reason, the current collector 4 can be used as a flow path to guide electrons to the terminal.

Here, the electrode for a magnesium ion secondary battery according to the present invention preferably has a configuration in which the positive electrode 1 contains WO _{3 in} particular. Therefore, in the region where the positive electrode 1 and the current collector 4 in FIG. 1 are bonded, the positive electrode 1 made of WO ₃ and the current collector 4 may be bonded as shown in FIG.

However, since WO ₃ is an insulator, the positive electrode 1 formed by aggregating only the powder particles of WO ₃ may make it difficult to pass a current from the positive electrode 1 to the current collector 4. It is preferred that the order positive electrode 1 as shown in FIG. 3 is a configuration in which the conductive additive 22 and powder particles of WO ₃ (WO ₃ powder 21) is secured by a binder 23.

  In this way, a current flows from the positive electrode 1 to the current collector 4 through the conductive additive 22 constituting the positive electrode 1. And the said electric current can be sent to the direction of a terminal by distribute | circulating the inside of the electrical power collector 4 in the left-right direction of FIG.

The crystal structure of the WO ₃ powder 21 is preferably a layered rock salt type structure. If it does in this way, the effect of enlarging the capacity | capacitance of the whole battery or improving cycling characteristics can be show | played. This is because a layered rock salt structure facilitates the desorption reaction and insertion reaction of tungsten ions associated with the charging / discharging of the battery.

The particles of the WO ₃ powder 21 preferably have a maximum particle size of 10 μm or less. Here, the particle diameter refers to the powder from the small particle diameter side to the large particle diameter side when the particle of the WO ₃ powder 21 is measured using a particle size distribution measurement method by a laser diffraction / scattering method. Means the value of the diameter of the powder cross-section at the location where the accumulated volume of 50% is 50%. More specifically the particle diameter distribution measuring method described above, by analyzing the scattering intensity distribution of laser light scattered light applied to the particles of the WO ₃ powder 21, a method of measuring the diameter of a particle of WO ₃ powder 21 It is.

  In the case of a magnesium ion secondary battery, the negative electrode 2 is preferably made of metallic magnesium. Magnesium is suitable for the material of the negative electrode 2 because it is easily oxidized.

  The separator 3 is preferably made of a material that is excellent in insulation, such as polyethylene and polypropylene, and that does not corrode by the electrolyte inside the battery container.

  The current collector 4 is preferably made of a material that is excellent in conductivity, such as aluminum, and that does not corrode by the electrolyte inside the battery.

When the thickness of the positive electrode 1 bonded to the current collector 4 (the horizontal dimension in FIG. 1 and the vertical dimension in FIGS. 2 and 3) is small, current flows in the direction along the thickness direction of the positive electrode 1 during discharge. Progresses and can immediately flow into the current collector 4. The current that has been able to flow into the current collector 4 travels in the up-down direction of FIG. 1 and the left-right direction of FIGS. Can do. Therefore, when the positive electrode 1 is relatively thin, the positive electrode 1 made only of the WO ₃ powder 21 as an insulating material may be formed as shown in FIG. However, when the positive electrode 1 is relatively thick, if the positive electrode 1 made only of the WO ₃ powder 21 that is an insulating material is formed, it may be difficult to pass a current from the positive electrode 1 to the current collector 4. For this reason, when the positive electrode 1 is relatively thick, it is preferable to use the positive electrode 1 made of an assembly of WO ₃ powder 21 and including a conductive additive 22 and a binder 23 as shown in FIG.

  Subsequently, each embodiment of the present invention using the general usage mode described above will be described.

(Embodiment 1)
The secondary battery according to Embodiment 1 is formed from a laminate 10 in which a plurality of positive electrodes 1 and negative electrodes 2 formed in a flat plate shape are laminated as shown in FIG. Here, the positive electrode 1 and the negative electrode 2 are laminated alternately, and the separator 3 is sandwiched between the positive electrode 1 and the negative electrode 2. However, the positive electrode 1 and the negative electrode 2 do not necessarily have to be stacked alternately (with the separator 3 in between). For example, after the positive electrode 1 has continued in two stages (with the separator 3 in between), the negative electrode 2 It may be a layered form that continues two steps).

As will be described later, the positive electrode 1 and the negative electrode 2 are connected to the above-described current collector 4 (see FIG. 1) in a partial region on the plane facing the separator 3. However, in order to make the figure easy to see, the current collector 4 is omitted in FIG. Here, the thickness of the positive electrode 1 (the thickness in the vertical direction in FIG. 4) is relatively thin, the current proceeds in the direction along the thickness direction inside the positive electrode 1, and the current is immediately applied to the current collector 4 (see FIG. 1). When it can flow, the positive electrode 1 may be composed of only the WO ₃ powder 21 (see FIG. 3). However, when the thickness of the positive electrode 1 is relatively large and it is difficult to immediately pass the current flowing in the direction along the thickness direction inside the positive electrode 1 to the current collector 4, the WO ₃ powder 21 as the active material is used. In addition, it is preferable that the conductive assistant 22 and the binder 23 are included.

The conductive additive 22 contained in the positive electrode 1 is preferably, for example, acetylene black or graphite (C) powder having a small average particle size of, for example, 0.1 μm or less. Thus, the conductive auxiliary agent 22 only by adding a small amount to the WO ₃ powder 21, it is possible to increase the utilization of the active material while suppressing a decrease in the electric capacity of the battery. In addition, the battery can be charged and discharged at high speed. Further, the proportion of the conductive auxiliary agent 22 to the whole positive electrode 1 is preferably 1% by mass or more and 20% by mass or less when acetylene black is used, and in the case of using the above-described small particle size graphite powder. Is preferably 1% by mass or more and 20% by mass or less.

The binder 23 for binding and integrating the plurality of WO ₃ powders 21 and the powder of the conductive additive 22 is a binder containing carbon or graphite (C). More specifically, for example, vinyl group fluorine-based organic compounds and the like can be mentioned. If a vinyl-based fluorine-based organic compound is used as the binder 23, the adhesion between the WO ₃ powder 21 and the conductive additive 22 can be strengthened and the particles of the WO ₃ powder 21 and the conductive additive 22 can be formed by adding a small amount of the binder 23. Occurrence of problems such as dropping off can be suppressed. Further, the binder 23 can strengthen the adhesion between the positive electrode 1 and the current collector 4. Furthermore, when the binder 23 comes into contact with the electrolytic solution of the battery, it is possible to suppress an undesirable reaction (side reaction).

Furthermore, since the binder 23 is bonded to a plurality of particles of the WO ₃ powder 21 and the particles of the conductive additive 22 to form an integrated electrode (positive electrode 1), the shape and strength of the positive electrode 1 can be maintained. If the binder 23 does not exist, a plurality of the particles of the WO ₃ powder 21 and the particles of the conductive auxiliary agent 22 are scattered randomly, and it becomes difficult to form a shape as the positive electrode 1. That is, when the positive electrode 1 includes the binder 23 made of a vinyl group organic compound, it is possible to form an arbitrary desired shape, for example, a rectangular structure, as the integral positive electrode 1.

  The ratio of the binder 23 to the whole positive electrode 1 is preferably 1% by mass or more and 40% by mass or less, particularly 1% by mass or more and 10% by mass when the above-described vinyl group fluorine-based organic compound is used. % Or less is more preferable.

Hereinafter, an example of a method for forming the positive electrode 1 will be described. The WO ₃ powder 21, acetylene black as the conductive additive 22, and polyvinylidene fluoride as the binder 23 have a mass ratio of 7: 2: 1. To mix. That is, mixing is performed so that the WO ₃ powder 21 is 70% by mass, the acetylene black as the conductive additive 22 is 20% by mass, and the polyvinylidene fluoride as the binder 23 is 10% by mass. This mixture is formed on an aluminum foil having a thickness of 20 μm and having dimensions in the vertical and horizontal directions corresponding to the size of the positive electrode 1 to be formed. Apply to. For this application, for example, a doctor knife is used. The aluminum foil coated with this mixture is dried by, for example, heating at 150 ° C. for 1 hour to desorb moisture in the mixture.

As described above, the particles of the WO ₃ powder 21 in the positive electrode 1 formed by drying the mixture here preferably have a maximum particle size of 10 μm or less, and more preferably 1 μm or less. By reducing the size of the particles of WO ₃ powder 21, sites magnesium ions during discharge and charge can be inserted into the area between the particles of WO ₃ powder 21 is increased. As a result, the electromotive force of the battery can be further increased.

  The negative electrode 2 may be made of a simple substance of magnesium metal, but may be made of, for example, a compound of magnesium and silicon (MgSi). The element of silicon has a function of suppressing the formation of a film made of oxygen on the surface of magnesium atoms when magnesium is oxidized. For this reason, the negative electrode 2 made of MgSi can ensure conductivity as an electrode.

  The laminated body 10 of FIG. 4 is wound in a spiral shape as shown in FIG. If the laminated body 10 is wound so that the spirally wound section forms a substantially circular shape as shown in FIG. 5, a substantially cylindrical shaped body is formed. In FIG. 5, the negative electrode 2 of FIG. 4 is arranged on the outer peripheral side of the cylindrical shape, and the positive electrode 1 of FIG. 4 is wound so as to be arranged on the inner peripheral side of the cylindrical shape. However, this is merely an example, and the positive electrode 1 is wound so as to be arranged on the outer peripheral side of the cylindrical shape, for example, depending on the shape and configuration of the battery container as the outer frame of the formed secondary battery. There may be.

  As shown in FIG. 5, the formed body formed by winding the laminate 10 composed of the positive electrode 1 and the negative electrode 2 is placed inside a battery container having a cylindrical shape, for example, so that the cylindrical magnesium ions shown in FIG. A secondary battery 100 is formed. Magnesium ion secondary battery 100 has a cylindrical shape similar to, for example, a nickel cadmium battery or a nickel metal hydride battery. In the magnesium ion secondary battery 100 of FIG. 6, the positive electrode terminal 5 is a terminal electrically connected to the positive electrode 1, and the negative electrode terminal 7 is a terminal electrically connected to the negative electrode 2.

  As shown in the cross-sectional view of FIG. 7, the magnesium ion secondary battery 100 is placed with the laminate 10 shown in FIG. 5 wound around it. However, although omitted in FIGS. 4 and 5, the actual magnesium ion secondary battery 100 includes the current collector 4 as shown in FIG. A magnesium ion secondary battery 100 of FIG. 6 has a positive electrode terminal 5 having a protruding shape that is smaller than the cross-sectional area of the battery container 12 with respect to the cross section intersecting the longitudinal direction (vertical direction) of FIG. And a flat negative electrode terminal 7 having substantially the same size as the cross-sectional area of 12. Therefore, as shown in FIG. 7, the current collector 4 is bonded to the positive electrode 1 at the upper end. Thus, the current passes from the positive electrode 1 through the current collector 4, and further reaches the gas discharge valve 13 and the positive electrode terminal 5 from the flow path above the current collector 4. On the other hand, as shown in FIG. 7, the current collector 4 is not disposed on the negative electrode 2, and the negative electrode 2 is in direct contact with the negative electrode terminal 7. However, the magnesium ion secondary battery 100 is not limited to such an embodiment. For example, the negative electrode terminal may have a protruding shape and the positive electrode terminal may have a flat shape. Alternatively, for example, the negative electrode may be provided with a flow path that leads to the negative electrode terminal via the current collector.

  A part of the region where the positive electrode 1 and the current collector 4 are bonded is surrounded by a dotted line in FIG. An enlarged view of the area surrounded by the dotted line corresponds to the above-described FIGS. In the central portion in the left-right direction in the cross-sectional view of FIG. 7, the depiction is omitted because the positive electrode 1 and the negative electrode 2 continue to be wound periodically with the separator 3 interposed therebetween.

  Although not considered in FIGS. 4 and 5, when the magnesium ion secondary battery 100 having the embodiment of FIG. 6 is actually formed, the sizes of the flat plate-like positive electrode 1 and negative electrode 2 to be stacked are formed. Is preferably changed. Specifically, as shown in FIG. 7, the negative electrode 2 is in direct contact with the negative electrode terminal 7, but the positive electrode 1 is preferably not in direct contact with the negative electrode terminal 7. In order to obtain such an aspect, it is preferable that the positive electrode 1 is slightly smaller than the negative electrode 2. In the gap region for preventing the positive electrode 1 from reaching the negative electrode terminal 7 by making the positive electrode 1 smaller than the negative electrode 2, for example, a separator 3 similar to the separator 3 sandwiched between the positive electrode 1 and the negative electrode 2 is disposed. It is preferable.

  The current collector 4 in FIG. 7 has a relatively short region bonded to the positive electrode 1 in the longitudinal direction (vertical direction in FIG. 7), but the length of the current collector 4 in the longitudinal direction is the length shown in FIG. It is not restricted to, It can be set as arbitrary length. However, the separator 3 is originally a member disposed in order to suppress a short circuit between the positive electrode 1 and the negative electrode 2 due to close contact. For this reason, as long as the separator 3 is disposed, the current collector 4 is preferably disposed so as to contact the positive electrode 1 only in a part of the region.

Furthermore, although not specifically illustrated in FIG. 7, a large number of members such as the positive electrode 1 and the negative electrode 2 are arranged inside the battery container 12, and an electrolytic solution is held so as to fill the inside. The electrolytic solution is preferably made of an organic solvent in which a magnesium salt is dissolved, and each member constituting the inside of the battery container 12 such as the positive electrode 1 and the negative electrode 2 is held so as to be immersed in the electrolytic solution. It is preferable. More specifically, the electrolytic solution is preferably, for example, RMgBr / THF (where R is a functional group of an organic compound, Br is bromine, and THF is tetrahydrofuran) or Mg (ClO ₄ ) ₂ / PC.

  Here, the operation principle of the magnesium ion secondary battery 100 will be described. As described above, at the time of discharging, current flows from the positive electrode 1 and flows from the current collector 4 through the gas discharge valve 13 to the connected load from the positive electrode terminal 5. In addition, current is fed back from the load to the negative electrode 2 through the negative electrode terminal 7. The flow of electrons is opposite to the current. That is, electrons flow into the positive electrode 1 and a reduction reaction occurs at the positive electrode 1. At this time, a large number of magnesium ions are contained in the material constituting the positive electrode 1. When charging, contrary to discharging, current flows out from the negative electrode 2, and current flows from the negative electrode terminal 7 to, for example, the negative electrode of the charger connected to the outside. A current flows out from the positive electrode of the charger and flows into the positive electrode 1 from the positive electrode terminal 5 of the magnesium ion secondary battery 100 through the gas discharge valve 13 and the current collector 4. At this time, the magnesium ion secondary battery 100 is charged by the magnesium ions moving to the flat negative electrode 2.

At this time, since the positive electrode 1 is made of a structure using the WO ₃ powder 21 as an active material, the reduction reaction of the positive electrode 1 when the magnesium ion secondary battery 100 is discharged becomes strong. This is because the positive electrode 1 contains a large amount of oxygen atoms, thereby increasing the oxidizing power of the positive electrode 1. Accordingly, the electromotive force (voltage) generated in the magnesium ion secondary battery 100 can be increased. Moreover, since the amount of movement of magnesium ions during charging and discharging increases, the cycle characteristics of the magnesium ion secondary battery 100 are improved. That is, the electrode (positive electrode) according to the present invention including WO ₃ can provide a magnesium ion secondary battery having higher voltage and better cycle characteristics. Specifically, for example, a conventional magnesium ion secondary battery in which the positive electrode is made of Mo ₆ S ₈ and the negative electrode is made of metal Mg has a discharge start voltage of 0.6 V, and the cycle of charging and discharging is repeated several times. As a result, the battery deteriorates. On the other hand, in the magnesium ion secondary battery in which the positive electrode of the present embodiment is made of WO ₃ and the negative electrode is made of metal Mg, the discharge start voltage is improved to 0.8 V, and the deterioration due to the cycle of charging and discharging is almost all. It became nothing.

  As a result, the electric capacity of the magnesium ion secondary battery 100 can be improved. Specifically, the electric capacity of the magnesium ion secondary battery 100 is preferably 10 Ah or more and 100 Ah or less.

  As shown in FIG. 7, gas may be generated inside the battery container 12 due to an oxidation-reduction reaction during charging or discharging of the magnesium ion secondary battery 100. For this reason, the magnesium ion secondary battery 100 is provided with a gasket 11 for suppressing leakage of gas, electrolyte, etc. and ensuring internal sealing, and a gas discharge valve 13 for discharging gas generated inside. Has been.

The results of charge / discharge evaluation using the magnesium ion secondary battery 100 described above are shown in FIG. The magnesium secondary battery subjected to the charge / discharge evaluation of FIG. 8 is a battery having an electric capacity of 10 Ah class and the battery container 12 formed of SUS304. In addition, the electrolytic solution disposed so as to be in contact with the positive electrode 1 and the negative electrode 2 in FIG. 7 in the battery is a solution in which bromine (Br) is added to a solution of Mg (ClO ₄ ) ₂ / PC.

  A discharge result 31 in FIG. 8 shows a result of a test in which such a battery is almost completely charged and connected to a load for discharge. 8 shows the result of a test in which the battery is connected to a charger and charged in a state where the battery is almost completely discharged. In the graph of FIG. 8, the horizontal axis indicates the elapsed time after the test is started in minutes, and the vertical axis is between the positive electrode terminal 5 and the negative electrode terminal 7 (see FIG. 6) of the battery under test. The voltage applied to is shown in volts. It can be seen from the discharge result 31 and the charge result 32 in FIG. 8 that the battery is sufficient for use as a magnesium secondary battery.

(Embodiment 2)
As shown in FIG. 9, the magnesium ion secondary battery 200 according to Embodiment 2 has a rectangular shape (cuboid shape) similar to that of a lithium ion battery, for example. In the magnesium ion secondary battery 100, the positive electrode terminal 5 is disposed at one end (upper side in FIG. 6) in the longitudinal direction, and the negative electrode terminal 7 is disposed at the other end (lower side in FIG. 6) in the longitudinal direction. . However, in the magnesium ion secondary battery 200, both the positive electrode terminal 5 and the negative electrode terminal 7 are disposed at one end portion (upper side in FIG. 9) in the longitudinal direction. In general, since many batteries have such a configuration, FIG. 9 shows a magnesium ion secondary battery 200 in which both terminals are arranged at one end. However, the present invention is not limited to this mode, and the magnesium ion secondary battery 200 of the second embodiment also has a rectangular shape, and the positive electrode terminal and the negative electrode terminal are arranged at the ends opposite to each other with respect to the longitudinal direction. Also good.

  For example, as shown in FIG. 4, instead of winding a plurality of flat positive electrodes 1, negative electrodes 2 and separators 3 in a spiral shape as shown in FIG. The magnesium ion secondary battery 200 having the cross-sectional shape of FIG. 10 or FIG. 11 may be formed by winding while forming. However, for example, the magnesium ion secondary battery 200 may be formed by arranging a plurality of laminated layers of the positive electrode 1, the negative electrode 2, and the separator 3 in the battery container 14 without being wound. .

  10 and 11, the current collector 4 disposed so as to contact the positive electrode 1 and the current collector 4 disposed so as to contact the negative electrode 2 are depicted one by one. Specifically, the current collector 4 that contacts the positive electrode 1 and exchanges electrical signals with the positive electrode 1 is the current collector 4 on the right side of FIG. 10 and the current collector 4 on the upper side of FIG. The current collector 4 that contacts the negative electrode 2 and exchanges electrical signals with the negative electrode 2 is the current collector 4 on the left side of FIG. 10 and the current collector 4 on the lower side of FIG. In this manner, each current collector 4 is depicted only one place at a time in order to make the drawing easier to see. Actually, the current collector 4 leading from each positive electrode 1 to the positive electrode terminal 5 and each negative electrode 2 to the negative electrode terminal are depicted. A current collector 4 leading to 7 is arranged. Further, the region surrounded by the dotted line in FIG. 10 corresponds to the above-described FIG. 2 and FIG.

  Further, in the magnesium ion secondary battery 200, expansion of the gap between the regions where the positive electrode 1, the negative electrode 2, and the separator 3 are laminated due to the gas generated by the oxidation-reduction reaction inside the battery container 14. In order to suppress this, it is preferable that the laminated body be pressed by the elastic body 24 from the upper side in FIG. In this way, it is possible to suppress the generation of unnecessary gaps inside the laminate.

  Further, for example, as shown in FIG. 12, the magnesium ion secondary battery 200 includes a separator 3 sandwiched between the upper positive electrode 1 and the lower negative electrode 2 in FIG. 12, an upper negative electrode 2 and a lower positive electrode. 1 is connected to and integrated with the separator 3 sandwiched between the positive electrode terminal 5 and the negative electrode terminal 7 on the opposite side (right side in FIG. 12). It may have the form which has. The magnesium ion secondary battery 200 of FIG. 12 also has the same operating principle as the magnesium ion secondary battery 200 of FIGS.

  Furthermore, even if a leaf spring type elastic body is used for the magnesium ion secondary battery 200, such as the elastic body 25 of FIG. 13, similarly to the crumaki spring type elastic body 24 as shown in FIG. The laminate can be pressed down. At this time, it is more preferable to sandwich the insulating plate-like member 6 between the elastic body 25 and the positive electrode 1 and press the laminated body through the insulating plate-like member 6. If it does in this way, a layered product can be pressed down more stably.

  The second embodiment of the present invention is different from the first embodiment of the present invention only in each point described above. That is, the configuration, conditions, procedures, effects, and the like that have not been described above for the second embodiment of the present invention are all in accordance with the first embodiment of the present invention.

(Embodiment 3)
Magnesium ion secondary batteries 100 and 200 of each embodiment described above are used in an electric power system. Specifically, a power system using magnesium ion secondary batteries 100 and 200 as a backup power source for a mobile phone base station can be provided.

  As shown in FIG. 14, the power system includes a transceiver 50 and an antenna 51. The transceiver 50 includes an amplifier 52, a controller 53, and a power supply unit 54. The power supply unit 54 includes a power supply system 55 and a backup power supply 56.

  Since the power system is for a mobile phone, the transceiver 50 has a role of communicating with the terminal of each mobile phone that is moving. A network mechanism 57 for connecting to an external network is connected to the controller 53. Radio waves received by the antenna 50 from one mobile phone terminal to the transceiver 50 are amplified by the amplifier 52, controlled for output by the controller 53, and then sent from the network mechanism 57 to another mobile phone terminal.

  The power source for performing the operation as described above is the power source unit 54. As the power source unit 54, a power source system 55 that normally uses power supplied from the outside as it is is used. However, for example, when the power supply system 55 becomes unusable due to a power failure or the like, power is supplied from the backup power supply 56.

  The magnesium ion secondary batteries 100 and 200 described above are used for the backup power source 56. In the case of the 27V-based magnesium ion battery system, as shown in FIG. 15, a single backup power supply 56 is formed by arranging a large number of battery cells 300 in series and in parallel. Although not specifically shown in FIG. 15, for example, eight battery cells 300 are arranged in series and 40 units are arranged in parallel, thereby forming one backup power source 56. Each battery constituting the battery cell 300 may be the magnesium ion secondary battery 100 or the magnesium ion secondary battery 200. These two kinds of magnesium ion secondary batteries may be mixed in one backup power source 56. A battery connected to these many battery cells 300 is connected to an external circuit at an input terminal 301 and an output terminal 302.

  Here, it is assumed that the electric capacity of one battery cell 300 (magnesium ion secondary batteries 100 and 200) is 50 Ah and the voltage of the one battery cell 300 is 3 to 4V. In this case, the backup power supply 56 in which the above-described eight battery cells 300 are arranged in series and in parallel with each other has an electric capacity of about 2000 Ah and a voltage of 27V. By using the magnesium ion secondary batteries 100 and 200 using the electrode (positive electrode) according to the present invention, the large electric capacity and voltage described above can be provided.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above-described embodiment but by the scope of claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

  The present invention is particularly excellent as a technique for improving the electric capacity, voltage, and cycle characteristics of a secondary battery.

1 positive, 2 negative, 3 a separator, 4 current collector, 5 a positive electrode terminal, 6 insulating plate-like member, 7 the negative terminal, 10 laminate, 11 gasket, 12, 14 battery container, 13 gas discharge valve, 21 WO ₃ powder , 22 Conductive aid, 23 Binder, 24, 25 Elastic body, 31 Discharge result, 32 Charge result, 50 Transmitter / receiver, 51 Antenna, 52 Amplifier, 53 Controller, 54 Power supply unit, 55 Power supply system, 56 Backup power supply, 57 Network Mechanism, 100, 200 Magnesium ion secondary battery, 300 battery cell, 301 input terminal, 302 output terminal.

Claims (9)

Comprising a WO _3, an electrode for a magnesium ion secondary battery. The electrode according to claim 1, comprising a conductive aid disposed around the WO ₃ particles.   The electrode according to claim 2, wherein a ratio of the conductive additive to the whole electrode is 1% by mass or more and 40% by mass or less. The electrode according to claim 2, further comprising a binder that joins the particles of the WO _{3 and} the particles of the conductive additive.   The electrode according to claim 4, wherein a ratio of the binder to the whole electrode is 1% by mass or more and 40% by mass or less. The electrode according to any one of claims 1 to 5, wherein the crystal structure of the WO ₃ is a layered rock salt structure.   A magnesium ion secondary battery using the electrode according to claim 1.   The magnesium ion secondary battery according to claim 7, wherein the magnesium ion secondary battery has an electric capacity of 10 Ah or more and 100 Ah or less.   An electric power system using the magnesium ion secondary battery according to claim 7.

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