JP5304961B1 - Negative electrode plate for magnesium ion secondary battery, magnesium ion secondary battery, and battery pack - Google Patents

Abstract

To further improve the charge / discharge efficiency of a magnesium ion secondary battery.
A negative electrode plate for a magnesium ion secondary battery includes a magnesium alloy having a body-centered cubic lattice structure.
[Selection] Figure 1

Description

  The present invention relates to a negative electrode plate for a magnesium ion secondary battery, a magnesium ion secondary battery, and a battery pack.

  In recent years, environmental problems such as global warming caused by an increase in carbon dioxide have become serious, and countermeasures are being promoted worldwide. In particular, active research and development on secondary batteries represented by lithium ion secondary batteries and the like as a clean energy source with a low environmental load are being promoted.

  Furthermore, recently, secondary batteries having higher energy density than lithium metal have been sought, and magnesium metal having higher energy density than lithium metal, resource-rich and superior safety is used. Various proposals for magnesium ion secondary batteries have been made.

  For example, Patent Document 1 can be cited as a prior art document relating to a magnesium ion secondary battery.

Japanese Patent No. 4973819

  The invention according to Patent Document 1 is an invention by the inventors of the present application, and the present invention aims to further improve the charge / discharge efficiency by devising the negative electrode plate of the magnesium ion secondary battery as in Patent Document 1. This is the main issue.

  The present invention for solving the above-described problems is a negative electrode plate for a magnesium ion secondary battery, and includes a magnesium alloy having a body-centered cubic lattice structure.

  In the above negative electrode plate for magnesium ion secondary battery, the magnesium alloy may be a magnesium-lithium alloy.

  Further, the present invention for solving the above problems is a magnesium ion secondary battery including a positive electrode plate, a negative electrode plate, and an electrolyte, and the negative electrode plate includes a magnesium alloy having a body-centered cubic lattice structure. It is characterized by.

  In the magnesium ion secondary battery, the magnesium alloy may be a magnesium-lithium alloy.

  Further, the present invention for solving the above problems includes a storage case, a magnesium ion secondary battery including a positive electrode terminal and a negative electrode terminal, and a protection circuit including an overcharge protection function and an overdischarge protection function. A battery pack configured by housing a magnesium ion secondary battery and the protection circuit in a case, wherein the magnesium ion secondary battery includes a positive electrode plate, a negative electrode plate, and an electrolyte. It includes a magnesium alloy having a body-centered cubic lattice structure.

  In the battery pack, the magnesium alloy may be a magnesium-lithium alloy.

  According to the negative electrode plate for a magnesium ion secondary battery of the present invention, charge / discharge efficiency can be improved. The same effect as described above can also be achieved by a magnesium ion secondary battery and a battery pack using the negative electrode plate for a magnesium ion secondary battery.

It is a schematic sectional drawing of the negative electrode plate for magnesium ion secondary batteries concerning the 1st Embodiment of this invention. It is a schematic sectional drawing of the negative electrode plate for magnesium ion secondary batteries concerning the 2nd Embodiment of this invention. It is a schematic sectional drawing of the negative electrode plate for magnesium ion secondary batteries concerning the 3rd Embodiment of this invention. It is a schematic sectional drawing which shows an example of the magnesium ion secondary battery of this invention. It is a schematic exploded view which shows an example of the battery pack of this invention. It is a figure which shows the result of having performed the charging / discharging test using the glass beaker cells 1-7 of each Example and each comparative example. It is an equilibrium diagram of a magnesium-lithium alloy. It is an equilibrium diagram of a magnesium-iron alloy.

<Negative electrode for magnesium secondary battery>
The negative electrode plate for magnesium ion secondary batteries of this invention is demonstrated concretely using drawing.

(First embodiment)
FIG. 1 is a schematic cross-sectional view of a negative electrode plate for a magnesium ion secondary battery according to the first embodiment of the present invention.

  As shown in FIG. 1, the negative electrode plate 10 for a magnesium ion secondary battery according to the first embodiment is characterized by being configured by an alloy plate including a magnesium alloy 11 having a body-centered cubic lattice structure. Yes. Thus, charge / discharge characteristics can be improved by using the magnesium alloy 11 having a body-centered cubic lattice structure as a material for the negative electrode plate.

  Here, as a material of the negative electrode plate for a magnesium ion secondary battery, the magnesium alloy 11 having a body-centered cubic lattice structure is filled as compared with a magnesium alloy having another structure such as a single element magnesium or a magnesium-aluminum alloy having a hexagonal close-packed structure. The reason why the discharge characteristics are excellent is not necessarily clear at the present time. However, magnesium itself is known to be a single phase of hexagonal close-packed structure, which is a crystal structure peculiar to magnesium metal, and magnesium-aluminum alloy is mainly characterized by hexagonal close-packed structure and aluminum metal. It is known that it is a mixed phase with a cubic close-packed structure (also called a face-centered cubic lattice structure) that is a crystal structure of Therefore, since the body-centered cubic lattice structure has a lower atomic filling rate than the six-method close-packed structure or the cubic close-packed structure, the insertion and desorption of magnesium ions in the crystal structure is performed smoothly. It can be considered that the charge / discharge characteristics are improved.

  Examples of the magnesium alloy 11 having a body-centered cubic lattice structure include an alloy of metal and magnesium having a body-centered cubic lattice structure when the metal is a simple substance. For example, in a magnesium-lithium alloy, when the lithium content is small, the hexagonal close-packed structure, which is a crystal structure peculiar to magnesium metal, is maintained. However, as the lithium content increases, crystals unique to lithium metal are maintained. It is known that the body-centered cubic lattice structure, which is part of the structure, undergoes a mixed phase of the body-centered cubic lattice structure and hexagonal close-packed structure, and then transitions to a single phase of the body-centered cubic lattice structure. . In the present embodiment, the magnesium alloy 11 having a body-centered cubic lattice structure is a concept that includes a magnesium alloy having any of a mixed phase including a body-centered cubic lattice structure and a single phase having a body-centered cubic lattice structure. is there.

  Examples of the metal having a body-centered cubic lattice structure when it is a single metal include lithium (Li), sodium (Na), potassium (K), vanadium (V), chromium (Cr), iron (Fe), rubidium ( Examples thereof include Rb), niobium (Nb), molybdenum (Mo), cesium (Ce), barium (Ba), tantalum (Ta), tungsten (W), and europium (Eu). A magnesium-lithium alloy having a body-centered cubic lattice structure and a magnesium-iron alloy having a body-centered cubic lattice structure are preferable because they are relatively easily available.

  Here, the composition of the magnesium alloy can be specified by inductively coupled plasma optical emission spectrometry (IPC-AES).

  Whether the magnesium alloy has a body-centered cubic lattice structure is checked by comparing the diffraction pattern obtained by the X-ray diffractometer (XRD) with the crystal structure data of the Inorganic Crystal Structure Database (ICSD). Can be specified. In addition to the above method, it is also possible to specify with reference to the composition ratio and the equilibrium diagram.

  The equilibrium diagram is also called a phase diagram, and shows the relationship between the crystal phase of the alloy and the content and temperature of the metal contained in the alloy, and shows the relationship between the metal necessary to obtain a specific crystal phase. By specifying the content ratio, or conversely, the crystal phase can be specified from the metal content ratio.

  FIG. 7 is an equilibrium diagram of a magnesium-lithium alloy. From FIG. 7, in the case of the magnesium-lithium alloy, when the mass of the entire magnesium-lithium alloy is 100%, a magnesium alloy having a body-centered cubic lattice structure is obtained by setting the lithium content ratio to 5.5% or more. I understand that

  FIG. 8 is an equilibrium diagram of a magnesium-iron alloy. As can be seen from FIG. 8, a magnesium-iron alloy having a body-centered cubic lattice structure can be obtained by including iron.

  The upper limit of the lithium content is not particularly limited. However, if there is too much lithium, there is a possibility that the electron density may decrease and the charge / discharge efficiency may be adversely affected. 50% or less is preferable. The reason for this is not necessarily clear at the present time. However, when Example 1 and Example 2 described later are compared, the mixed phase including the body-centered cubic lattice structure is better than the single phase of the body-centered cubic lattice structure. Moreover, since the result which is excellent in charging / discharging characteristic is obtained, it is preferable to make the content rate of lithium into 10.5% or less.

  In the present embodiment, the thickness of the negative electrode plate 10 for a magnesium ion secondary battery is not particularly limited, but may be, for example, about 10 μm to 100 μm.

(Second Embodiment)
FIG. 2 is a schematic cross-sectional view of a negative electrode plate for a magnesium ion secondary battery according to a second embodiment of the present invention.

  As shown in FIG. 2, the negative electrode plate 20 for a magnesium ion secondary battery according to the second embodiment includes an alloy plate containing a magnesium alloy 11 having a body-centered cubic lattice structure and a support substrate 12 for supporting the alloy plate. It is characterized by being constructed. The negative electrode plate for a magnesium ion secondary battery does not need to have a single-layer structure consisting only of an alloy plate containing a magnesium alloy 11 having a body-centered cubic lattice structure as shown in FIG. 1, but the alloy plate as shown in FIG. A laminated structure in which the support substrate 12 and the support substrate 12 are laminated.

  In the magnesium alloy 11 having a body-centered cubic lattice structure as a material of the alloy plate in the negative electrode plate 20 for a magnesium ion secondary battery according to the second embodiment, the body-centered cubic lattice structure constituting the alloy plate in FIG. Since this is the same as the magnesium alloy 11, description thereof is omitted here.

  Examples of the support substrate 12 in the negative electrode plate 20 for a magnesium ion secondary battery according to the second embodiment include an aluminum substrate, a nickel substrate, a magnesium substrate, a titanium substrate, a copper substrate, and a carbon plate. The thickness of the support substrate 12 is not particularly limited, but may be, for example, about 10 μm to 100 μm, and further may be about 10 μm to 50 μm.

(Third embodiment)
FIG. 3 is a schematic cross-sectional view of a negative electrode plate for a magnesium ion secondary battery according to a third embodiment of the present invention.

  As shown in FIG. 3, in the negative electrode plate 30 for a magnesium ion secondary battery according to the third embodiment, alloy particles 11 containing magnesium having a body-centered cubic lattice structure are solidified by a binder resin 13 on a support substrate 12. It has a configuration in which magnesium alloy layers are laminated. Thus, the magnesium alloy 11 having a body-centered cubic lattice structure in the negative electrode plate for a magnesium ion secondary battery does not necessarily need to be an alloy plate, and may be in the form of particles, which may be solidified with a binder resin.

  Since the magnesium alloy 11 having a body-centered cubic lattice structure and the support substrate 12 which are the materials of the alloy layer according to the third embodiment are the same as those in the first embodiment and the second embodiment, description thereof is omitted here. To do.

  In forming the negative electrode plate 30 for a magnesium ion secondary battery according to the third embodiment, for example, a coating solution in which the magnesium alloy 11 having a body-centered cubic lattice structure and the binder resin 13 are dissolved or dispersed in an appropriate solvent. This can be obtained by coating and drying this on the surface of the support substrate 13. Examples of the binder resin used here include organic polymer compounds such as polyvinylidene fluoride.

  Although not shown, it is also possible to give a predetermined support to the magnesium-lithium alloy layer in which the alloy particles containing the magnesium-lithium alloy 11 are hardened with the binder resin 13 by pressing or the like. In this case, For this, the support substrate 12 may not be used.

<Magnesium ion secondary battery>
Next, the magnesium ion secondary battery of the present invention will be described with reference to FIG.

  FIG. 4 is a schematic cross-sectional view showing an example of the magnesium ion secondary battery 100 of the present invention.

  As shown in FIG. 4, the magnesium ion secondary battery 100 of the present invention includes a positive electrode plate 40 and a negative electrode plate 50 combined with the positive electrode plate 40, and these are accommodated in a container formed of an exterior 81. The container is sealed with the electrolyte 90 filled in the container.

  Here, the magnesium ion secondary battery 100 of the present invention is characterized in that the negative electrode plate 50 is the negative electrode plate (10, 20, and 30) of the present invention described above. Specifically, the negative electrode plate includes a magnesium alloy having a body-centered cubic lattice structure. The magnesium ion secondary battery 100 of the present invention is not particularly limited with respect to other requirements as long as it has this requirement, and a conventionally known positive electrode plate, electrolyte, and container are appropriately selected in the field of magnesium ion secondary batteries. The present invention is not limited to the form shown in FIG. As the negative electrode plate 50, the negative electrode plate of the present invention described above can be used as it is, and description thereof is omitted here.

  The positive electrode plate 40 is usually composed of a positive electrode substrate and a positive electrode material provided on the positive electrode substrate. Examples of the positive electrode substrate include an aluminum plate, a copper plate, a titanium plate, a nickel plate, and a stainless plate having a thickness of about 10 to 100 μm.

The positive electrode material only needs to be able to reversibly insert and desorb magnesium ions. For example, such a positive electrode material includes graphite fluoride ((CF) _n ), manganese dioxide (MnO ₂ ). And manganese oxide, and vanadium oxide such as divanadium pentoxide (V ₂ O ₅ ).

  The electrolyte 90 is not particularly limited, and an electrolytic solution using an aqueous solvent or an organic solvent, an ionic liquid, a solid electrolyte, a gel electrolyte, or the like can be used.

As an example of the electrolyte, known electrolytes capable of inserting and removing magnesium ions, for example, Grignard reagent (RMgX: R is an alkyl group or an aryl group, Mg is magnesium, X is iodine, bromine, And an ether solution of magnesium bis (trifluoromethanesulfone) imide (Mg (TFSI) ₂ ) in propylene carbonate or a dimethoxyethane solvent. According to the magnesium ion secondary battery 100 of the present invention, when these electrolytes are used, an improvement in charge / discharge efficiency and an improvement in cycle characteristics are expected as compared with the case where a conventionally known negative electrode plate is used. .

  As a structure of the magnesium ion battery manufactured using the positive electrode plate, the negative electrode plate 50 of the present invention, and the electrolyte 90, a conventionally known structure can be appropriately selected and used. For example, the structure which winds a positive electrode plate and a negative electrode plate in the shape of a spiral via the separator like the polyethylene-made porous film which is not shown in figure, and accommodates in a battery container is mentioned. As another aspect, a structure in which a positive electrode plate and a negative electrode plate cut into a predetermined shape are stacked and fixed via a separator, and this is housed in a battery container may be employed. In any structure, after the positive electrode plate and the negative electrode plate are stored in the battery container, the lead wire attached to the positive electrode plate is connected to the positive electrode terminal provided in the outer container, while the lead wire attached to the negative electrode plate Is connected to a negative electrode terminal provided in the exterior container, and the battery container is further filled with an electrolyte 90, and then sealed to produce a magnesium ion secondary battery. In addition, when using solid electrolyte, gel electrolyte, etc. as the electrolyte 90, a separator can be made unnecessary.

(Battery pack)
Next, a battery pack 200 configured using the magnesium ion secondary battery 100 of the present invention will be described with reference to FIG.

  FIG. 5 is a schematic exploded view showing an example of the battery pack 200 of the present invention.

  As shown in FIG. 5, the battery pack 200 is configured by storing the magnesium ion secondary battery 100 in a resin container 36 a, a resin container 36 b, and an end case 37. Further, a protective circuit board 34 for preventing overcharge and overdischarge between one end face of the magnesium ion secondary battery and a face including the positive electrode terminal 32 and the negative electrode terminal 33 and the end case 37. Is provided.

  The protection circuit board 34 includes an external connection connector 35. The external connection connector 35 is connected to an external connection window 38a provided in the resin container 36a and an external connection window 38b provided in the end case 37. Inserted and connected to external terminals. The protection circuit board 34 includes a charge / discharge safety circuit (not shown) for controlling charge / discharge, a wiring circuit for connecting the external connection terminal and the magnesium ion secondary battery 100, and the like.

  The battery pack 200 can appropriately select a configuration of a conventionally known battery pack except that the magnesium ion secondary battery 100 of the present invention is used. Although not shown, the battery pack 200 includes a positive electrode lead plate connected to the positive electrode terminal 32, a negative electrode lead plate connected to the negative electrode terminal 33, an insulator, and the like between the magnesium ion secondary ground 100 and the end case 37. It may be provided as appropriate.

  In addition, the magnesium ion secondary battery 100 of the present invention has a function of blocking the excessive current, monitoring the battery temperature, etc., in addition to the use mode for the battery pack, and the protection circuit includes the magnesium ion. You may use for the aspect attached to the secondary battery 100 integrally. In such an embodiment, the battery pack can be used as a magnesium ion secondary battery including a protection function and a protection circuit without constituting a battery pack, and is highly versatile. In addition, some aspects demonstrated above are only illustrations, and do not limit the use of the negative electrode plate 50 of this invention, or the magnesium ion secondary battery 200 of this invention at all.

  Next, the present invention will be described more specifically with reference to examples and comparative examples. Hereinafter, unless otherwise specified, parts or% is based on mass.

Example 1
Creation of positive electrode plate 1;
Copper molybdenum sulfide (Cu ₂ Mo ₆ S ₈ ): 5 g, acetylene black: 0.3 g, carbon nanotube (manufactured by Showa Denko KK: VGCF (registered trademark)) 0.2 g, KF polymer: 6 g, and N-methyl Pyrrolidone (NMP): 4 g was mixed and stirred for 5 minutes at 8000 rpm with an Excel auto homogenizer (Nippon Seiki Seisakusho Co., Ltd.) to obtain ink for positive electrode plate 1. This ink was applied on a copper substrate having a thickness of 10 μm with an applicator having a gap of 200 μm, dried at 150 ° C., and then pressed at 2 ton / cm to obtain a positive electrode plate 1.

Creation of negative electrode plate 1;
A magnesium-lithium alloy having a thickness of 40 μm (9% by mass of lithium, 1% by mass of zinc, the balance being magnesium and a mixed phase of a body-centered cubic lattice structure and a hexagonal close-packed structure) was prepared. It was.

Preparation of electrolyte 1;
In a glove box filled with an inert atmosphere, phenylmagnesium chloride / 2 mol tetrahydrofuran solution (manufactured by Tokyo Chemical Industry Co., Ltd.) and aluminum chloride are mixed in a molar ratio of 2: 1, and the concentration in the tetrahydrofuran solution is 0.25 mol / l. It was set as the electrolyte 1 by preparing to.

Creation of glass beaker cell 1;
The glass beaker cell 1 of Example 1 was assembled using the positive electrode plate 1 prepared above as the working electrode, the negative electrode plate 1 prepared above as the counter electrode and the reference electrode plate, and the electrolyte 1 prepared above as the electrolyte. . All assembly and liquid injection operations were performed in a glove box filled with an inert atmosphere.

(Example 2)
A magnesium-lithium alloy having a thickness of 500 μm (14% by mass of lithium, 1% by mass of aluminum, the balance being magnesium and a single phase of a body-centered cubic lattice structure) was prepared, and all the same except that this was used as the negative electrode plate 2 The glass beaker cell 2 concerning Example 2 was created in the way of these.

(Comparative Example 1)
A magnesium-aluminum alloy having a thickness of 45 μm (aluminum 3 mass%, zinc 1 mass%, the balance being magnesium and a mixed phase of hexagonal close-packed structure and cubic close-packed structure) was prepared. The glass beaker cell 3 concerning the comparative example 1 was created in the same way except having carried out.

(Comparative Example 2)
Comparative Example 2 except that a magnesium-nickel alloy having a thickness of 200 μm (less than 3% by mass of nickel, the balance being magnesium and hexagonal Mg ₂ Ni) was prepared and used as the negative electrode plate 4. A glass beaker cell 4 was prepared.

(Comparative Example 3)
A magnesium-aluminum alloy (6% by mass of aluminum, 0.3% by mass of manganese, the balance being magnesium and a mixed phase of hexagonal close-packed structure and cubic close-packed structure) having a thickness of 300 μm was prepared, and this was prepared as a negative electrode plate A glass beaker cell 5 according to Comparative Example 3 was prepared in the same manner except that the number was 5.

(Comparative Example 4)
A glass beaker cell 6 according to Comparative Example 4 was prepared in the same manner except that a pure magnesium metal (single phase having a hexagonal close-packed structure) with a thickness of 250 μm was prepared and used as the negative electrode plate 6.

(Comparative Example 5)
Comparative Example 5 except that a magnesium-lithium alloy having a thickness of 200 mm (lithium 5% by mass, the balance being magnesium, a single phase having a hexagonal close-packed structure) was prepared, and this was used as the negative electrode plate 7. A glass beaker cell 7 was prepared.

Charging / discharging test The charging / discharging test was done using the glass beaker cells 1-7 of each Example and each comparative example. The charge / discharge test was performed in a voltage range of 0.3 V to 1.7 V, and it was confirmed whether charging / discharging was possible using the glass beaker cells 1 to 7 of the examples and comparative examples. The current density was 6.25 μA / cm ² in all cases.

(result)
Drawing 6 is a figure showing the result of having performed a charge-and-discharge test using glass beaker cells 1-7 of each example and each comparative example.

  As shown in FIG. 6, in the glass beaker cells 1 and 2 of Examples 1 and 2, the discharge voltage was about 1.1 V, but in the glass beaker cells 3 to 7 of Comparative Examples 1 to 5, the discharge voltage was Both were less than 1V. Further, in the glass beaker cells 1 and 2 of Examples 1 and 2, the discharge capacity was about 127 mAh / g, but in the glass beaker cells 3 to 7 of Comparative Examples 1 to 5, both were 90 mAh / g or less. It was.

DESCRIPTION OF SYMBOLS 10, 20, 30 ... Negative electrode plate for magnesium ion secondary batteries 11 ... Magnesium alloy of body centered cubic lattice 12 ... Support substrate 13 ... Binder resin 50 ... Negative electrode plate 32 ... Positive terminal 33 ... Negative terminal 34 ... Protection circuit board 35 ... External connector 36a, 36b ... Resin container 37 ... End case 38a, 38b ... External connection window 40 ... Positive electrode plate 81 ... Exterior 100 ... Magnesium ion secondary battery 200 ... Battery pack

Claims (6)

  A negative electrode plate for a magnesium ion secondary battery, comprising a magnesium alloy having a body-centered cubic lattice structure.   The negative electrode plate for a magnesium ion secondary battery according to claim 1, wherein the magnesium alloy is a magnesium-lithium alloy. A magnesium ion secondary battery including a positive electrode plate, a negative electrode plate, and an electrolyte,
The magnesium ion secondary battery, wherein the negative electrode plate includes a magnesium alloy having a body-centered cubic lattice structure.   The magnesium ion secondary battery according to claim 3, wherein the magnesium alloy is a magnesium-lithium alloy. A storage case, a magnesium ion secondary battery including a positive electrode terminal and a negative electrode terminal, and a protection circuit including an overcharge protection function and an overdischarge protection function, and the magnesium ion secondary battery and the protection circuit are stored in the storage case A battery pack comprising:
The magnesium ion secondary battery includes a positive electrode plate, a negative electrode plate, and an electrolyte,
The negative electrode plate includes a magnesium alloy having a body-centered cubic lattice structure.   The battery pack according to claim 5, wherein the magnesium alloy is a magnesium-lithium alloy.

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