WO2018168995A1 - Electrode provided with alloy layer of magnesium and bismuth, and magnesium secondary battery - Google Patents

Electrode provided with alloy layer of magnesium and bismuth, and magnesium secondary battery Download PDF

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WO2018168995A1
WO2018168995A1 PCT/JP2018/010207 JP2018010207W WO2018168995A1 WO 2018168995 A1 WO2018168995 A1 WO 2018168995A1 JP 2018010207 W JP2018010207 W JP 2018010207W WO 2018168995 A1 WO2018168995 A1 WO 2018168995A1
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magnesium
bismuth
electrode
alloy
secondary battery
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PCT/JP2018/010207
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French (fr)
Japanese (ja)
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信子 吉本
一大 山吹
加成恵 板岡
藤井　健太郎
敏治 松本
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国立大学法人山口大学
株式会社戸畑製作所
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Priority to JP2019506260A priority Critical patent/JP6958823B2/en
Publication of WO2018168995A1 publication Critical patent/WO2018168995A1/en

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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C12/00—Alloys based on antimony or bismuth
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C23/00—Alloys based on magnesium
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to an electrode including an alloy layer of magnesium and bismuth, and a magnesium secondary battery including the electrode.
  • lithium ion secondary batteries have been put into practical use as secondary batteries and are used in various applications such as electronic devices.
  • Magnesium not only has an electric capacity per volume about twice that of lithium, but also has a melting point as high as 650 ° C. compared to 186 ° C. of lithium.
  • the lithium ion secondary battery has been pointed out to be heated and ignited by a short circuit inside the battery. One of the causes is a low melting point of lithium.
  • magnesium has a higher melting point than lithium, and therefore has high safety.
  • Magnesium is more abundant on the earth than lithium, which is a rare metal, and is abundant in resources.
  • the conventional magnesium negative electrode has an oxide film as an insulating layer formed on the surface thereof, there is a problem that it is difficult for electricity to flow, the overvoltage becomes large, and the original battery capacity characteristics cannot be exhibited.
  • Non-Patent Document 1 a method of removing the oxide film on the surface of the magnesium negative electrode using EtMgBr / THF as an electrolytic solution.
  • this method has a problem that it is not resistant to the potential on the oxidation side and the electrolytic solution is decomposed, so that charging / discharging for a long time cannot be performed.
  • the positive electrode materials that can be used are limited, and only low-potential batteries with a voltage of about 1 V have been reported.
  • An object of the present invention is to solve the above-mentioned problems, suppress the formation of an oxide film, and produce an electrode capable of producing a high-potential and high-capacity magnesium secondary battery; It is to provide a secondary battery.
  • magnesium electrode itself from the elements constituting the magnesium secondary battery and started development.
  • Magnesium was alloyed with bismuth at an arbitrary ratio, and its electrochemical characteristics were evaluated as a negative electrode of a magnesium secondary battery.
  • an alloy with a smaller amount of bismuth was formed. As a result, it was found that the formation of an oxide film is suppressed, and it can be used as an electrode for a magnesium secondary battery having a high potential and a high capacity.
  • the magnesium-bismuth alloy electrode reported so far is a brittle intermetallic compound (Mg 3 Bi 2 ) and has poor electrode forming characteristics.
  • conductive carbon and a binder (binder) In order to function as an electrode, the content of magnesium having a high capacity is remarkably reduced (Mg content is 13% by mass or less).
  • Mg content is 13% by mass or less.
  • the present inventors have found that an electrode material having excellent forming characteristics can be obtained by setting the composition in the alloy to a state in which there are many Mg—Bi solid solutions or Mg—Mg 3 Bi 2 eutectics.
  • An electrode comprising an alloy layer of magnesium (Mg) and bismuth (Bi), wherein the alloy layer is a solid solution of magnesium (Mg) and bismuth (Bi) (Mg 1-x Bi x ; x includes 0.001 to 0.0112) or a solid solution of magnesium (Mg) and bismuth (Bi) (Mg 1-x Bi x ; where x is 0.001 to 0.0112) and magnesium (Mg ) And an bismuth (Bi) intermetallic compound (Mg 3 Bi 2 ).
  • a magnesium secondary battery comprising the electrode according to (1) or (2) as a negative electrode, and further comprising an electrolyte layer and a positive electrode.
  • the electrode of the present invention can increase the magnesium content while suppressing the formation of an oxide film. Moreover, it can process into the form which can be used as an electrode, without requiring a binder and a conductive support agent. Since the magnesium secondary battery of this invention can suppress formation of an oxide film, it can suppress an overvoltage and can obtain a secondary battery with a high potential and a high capacity.
  • FIG. 3 is a diagram showing cyclic voltammetry of a magnesium-bismuth alloy having a bismuth content of 2 mass% in Example 1.
  • FIG. 3 is a view showing cyclic voltammetry of a magnesium-bismuth alloy having a bismuth content of 30% by mass in Example 1.
  • FIG. 3 is a diagram showing cyclic voltammetry of a magnesium-bismuth alloy having a bismuth content of 50% by mass in Example 1. It is a figure which shows the cyclic voltammetry of magnesium whose bismuth content in the comparative example 1 is 0 mass%.
  • 6 is a diagram showing a configuration of a magnesium secondary battery produced in Example 2.
  • FIG. 6 is a diagram showing the results of charge / discharge measurement of a magnesium secondary battery produced in Example 2.
  • FIG. 6 is a diagram showing the results of charge / discharge measurement of a magnesium secondary battery produced in Comparative Example 2.
  • FIG. 1 is a diagram showing cyclic voltammetry of a magnesium-
  • the electrode of the present invention is an electrode having an alloy layer of magnesium and bismuth, wherein the alloy contains a solid solution of magnesium and bismuth, or contains a solid solution of magnesium and bismuth and an intermetallic compound of magnesium and bismuth.
  • the phrase “containing a solid solution of magnesium and bismuth and an intermetallic compound of magnesium and bismuth” includes the case where the solid solution of magnesium and bismuth and the intermetallic compound are present in the alloy in the form of a eutectic structure.
  • metal Mg and Mg—Bi are used until the Bi content of the alloy is 8.87 mass% (1.12 at%), which is the solid solubility limit.
  • Mg—Bi solid solution and Mg—Mg 3 Bi 2 eutectic are formed from 8.87 mass% (1.12 at%) to the eutectic point of 58.9 mass% (14.3 at%).
  • an Mg—Mg 3 Bi 2 eutectic and an Mg 3 Bi 2 intermetallic compound are formed, and 82.2 mass% (35 at%) or more is known to form a Mg 3 Bi 2 intermetallic compound, a Bi—Mg solid solution, and metal Bi, and the form of the structure varies depending on the production conditions.
  • the alloy of magnesium and bismuth in the present invention includes a solid solution of magnesium and bismuth, or a solid solution of magnesium and bismuth and an intermetallic compound of magnesium and bismuth. That is, the composition of the magnesium alloy in the present invention includes the form in which the metallic Mg and Mg—Bi solid solution coexist, the form in which the Mg—Bi solid solution and Mg—Mg 3 Bi 2 eutectic coexist, and the Mg—Mg 3 Bi 2 eutectic. And Mg 3 Bi 2 intermetallic compound are included.
  • the content of bismuth in the magnesium alloy in the present invention is such that the battery reaction involves dissolution-precipitation of the metal Mg and Mg—Bi solid solution, so that no solid solution is formed in the alloy from the viewpoint of increasing the electric capacity per volume. 58.9 mass% or less is preferable with respect to the whole magnesium alloy, and 50 mass% or less is more preferable.
  • the bismuth content of the magnesium alloy is preferably 1 to 50% by mass with respect to the entire magnesium alloy from the viewpoint of workability of the magnesium alloy.
  • the bismuth content of the magnesium alloy in the present invention is preferably 1 to 58.9% by mass, and preferably 1 to 50% by mass, based on the entire magnesium alloy, from the viewpoint of the effect of suppressing the formation of an oxide film. More preferably, the content is 30 to 50% by mass.
  • x is preferably in the range of 0.001 or more which is the lower limit that can substantially exist as a solid solution and 0.0112 or less which is the solid solution limit.
  • the alloy layer in the electrode of the present invention contains a solid solution of Mg (Mg) and bismuth (Bi) (Mg 1-x Bi x ; where x is 0.001 to 0.0112), or magnesium (Mg) and Includes a solid solution with bismuth (Bi) (Mg 1-x Bi x ; x is 0.001 to 0.0112), an intermetallic compound (Mg 3 Bi 2 ) of magnesium (Mg) and bismuth (Bi) .
  • the processed form of the magnesium alloy itself is used as an electrode or attached to a current collector as an electrode. Can be used. Therefore, as in the case of using a granular electrode material, the electrode can be produced without the need for a binder or a conductive additive, and therefore the electrode can be produced without reducing the magnesium content in the electrode.
  • the electrode may be produced by processing the magnesium alloy into a scale shape, a flat shape, a spindle shape, a spherical shape, or the like, mixing with a binder, and fixing on the current collector.
  • the “magnesium alloy layer” in the present invention means a layer containing a magnesium alloy in the present invention, and the magnesium alloy in the present invention is processed into a plate shape, a columnar shape, etc., and the magnesium alloy itself forms a magnesium alloy layer. And the case where the magnesium alloy particles are fixed with a binder or the like to form a magnesium alloy layer.
  • the “electrode having a magnesium alloy layer” in the present invention is only required that the electrode has the magnesium alloy layer, and when the electrode is composed of only the magnesium alloy layer, the magnesium alloy layer and the current collector, etc. This includes the case where the electrode is configured together with other components.
  • the battery of the present invention includes the electrode of the present invention as a negative electrode, and further includes an electrolyte layer and a positive electrode.
  • What is used for the conventional magnesium secondary battery can be used for the positive electrode in the battery of this invention, electrolyte, and another component as needed.
  • examples of the positive electrode include those in which a positive electrode active material is fixed on a current collector by a binder, and may include a conductive aid as necessary.
  • positive electrode active material for example, sulfur or sulfur compounds, V 2 O 5, sulfur-doped V 2 O 5 or the like V 2 O 5 system, MnO 2 system, MnO 3, MgMnO oxides such as MnO 3 system, such as 3 Positive electrode of sulfide type, positive electrode of sulfide type such as Mo 6 S 8 type, Mg 1.03 Mn 0.97 SiO 4 , MgCoSiO 4 , MgFeSiO 4 , MgMnSiO 4, Mo 9 Se 11 , FePO 4 and the like. .
  • binder examples include fluorine-containing resins such as polyvinylidene fluoride and polytetrafluoroethylene, and resin materials such as styrene butadiene rubber and carboxymethyl cellulose.
  • conductive assistant examples include graphite such as amorphous carbon, natural graphite, and artificial graphite, carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black, and carbon nanotube. Examples include carbonaceous materials.
  • Examples of the electrolyte include magnesium halides such as magnesium perchlorate (Mg (ClO 4 ) 2 ), Grignard reagent (RMgX (R is an organic group, X is a halogen)), magnesium bromide (MgBr 2 ), and the like.
  • magnesium halides such as magnesium perchlorate (Mg (ClO 4 ) 2 ), Grignard reagent (RMgX (R is an organic group, X is a halogen)
  • magnesium bromide MgBr 2
  • electrolyte solvent known non-aqueous electrolyte solvents can be used.
  • acetonitrile dietochiethane
  • diethylene glycol dimethyl ether diglyme
  • triethylene glycol dimethyl ether triglyme
  • tetraglyme tetraglyme
  • tetrahydrofuran THF
  • propylene carbonate PC
  • ethylene carbonate butylene carbonate, vinylene carbonate, ⁇ -butyllactone
  • sulfolane 1,2-dimethoxyethane, 1,2-diethoxyethane, 2-methyltetrahydrofuran, 3-methyl-1 , 3-dioxolane, methyl propionate, methyl butyrate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate and the like.
  • Example 1 Pretreatment of electrodes
  • Mg-Bi alloy magnesium-bismuth alloy according to the present invention having a bismuth (Bi) content of 2% by mass, 30% by mass, and 50% by mass is cut into a cylindrical shape having a diameter of 7 mm and a thickness of 2 mm. Both surfaces of the metal piece were polished in the order of emery paper # 220, 600, 2000 to obtain a test piece.
  • the potential difference at the rise of the oxidation-reduction response due to dissolution-precipitation of magnesium is 2 V or more. This is an effect of the oxide film formed on the surface of the magnesium electrode.
  • the Mg—Bi alloy of the example is used as a test piece, as shown in FIGS. 1 to 3, the potential difference at the start of the oxidation-reduction response is small, particularly when the Bi content is 30% by mass or more. An oxidation-reduction response has been observed. Thus, it can be seen that the formation of the oxide film was suppressed in the Mg—Bi alloy of the example.
  • the magnesium content of the Mg—Bi alloy of the example is 98 to 50% by mass, and is extremely large, for example, compared to 16% by mass of the magnesium content in the Mg 3 Bi 2 intermetallic compound.
  • the results of charge / discharge measurement of a magnesium-sulfur battery showed that a high-potential discharge behavior was obtained as compared with a normal pure magnesium metal negative electrode.
  • the suppression effect of the magnesium oxide film in the negative electrode was confirmed.
  • the discharge capacity also reached the theoretical capacity of sulfur.
  • the electrode of the present invention suppresses the formation of an oxide film on the electrode surface and has a high magnesium content, it can be suitably used for a magnesium secondary battery, suppresses overvoltage, and has a high potential and high capacity. A secondary battery can be obtained.
  • the electrode of this invention uses a magnesium alloy as an electrode material, it has sufficient intensity

Abstract

The present invention addresses the problem of providing: an electrode which enables the production of a magnesium secondary battery that is suppressed in the formation of an oxide coating, while having high potential and high capacity; and a magnesium secondary battery which is suppressed in the formation of an oxide coating, while having high potential and high capacity. An electrode which is characterized by containing a solid solution (Mg1-xBix, wherein x is 0.001-0.0112) of magnesium (Mg) and bismuth (Bi) or by containing a solid solution (Mg1-xBix, wherein x is 0.001-0.0112) of magnesium (Mg) and bismuth (Bi) and an intermetallic compound (Mg3Bi2) of magnesium (Mg) and bismuth (Bi). A magnesium secondary battery that is characterized by being provided with this electrode, which serves as a negative electrode, while being additionally provided with an electrolyte layer and a positive electrode.

Description

マグネシウムとビスマスの合金層を備える電極及びマグネシウム二次電池Electrode comprising magnesium and bismuth alloy layer and magnesium secondary battery
　本発明は、マグネシウムとビスマスの合金層を備える電極、及び前記電極を備えるマグネシウム二次電池に関する。 The present invention relates to an electrode including an alloy layer of magnesium and bismuth, and a magnesium secondary battery including the electrode.
　近年、二次電池としてリチウムイオン二次電池が実用化され、電子デバイス等の様々な用途に使用されている。しかしながら、今後の車載用途や大型用途に対しては、リチウムイオン二次電池では対応することが難しく、他の二次電池の開発が行われている。そこで、体積当たりの電気容量でリチウムイオン二次電池を凌ぐ特性を有するマグネシウム二次電池の開発が盛んに行われている。マグネシウムは、体積当たりの電気容量がリチウムの約２倍であるだけでなく、融点がリチウムの１８６℃に比べて６５０℃と高い。リチウムイオン二次電池は、電池内部での短絡等により加熱、発火するとの問題が指摘されているが、この原因の一つとしてリチウムの融点の低さが挙げられている。この点、マグネシウムはリチウムに比べて融点が高いため、安全性が高い。また、マグネシウムは、希少金属であるリチウムに比べて地球上に多く存在し、資源的にも豊富である。しかし、従来のマグネシウム負極は、その表面に絶縁層である酸化皮膜が形成されるため、電気が流れにくく過電圧が大きくなり、本来の電池容量特性が発揮できないとの問題があった。 In recent years, lithium ion secondary batteries have been put into practical use as secondary batteries and are used in various applications such as electronic devices. However, it is difficult to deal with future in-vehicle applications and large-scale applications with lithium ion secondary batteries, and other secondary batteries are being developed. Therefore, development of magnesium secondary batteries having characteristics that surpass lithium ion secondary batteries in terms of electric capacity per volume has been actively conducted. Magnesium not only has an electric capacity per volume about twice that of lithium, but also has a melting point as high as 650 ° C. compared to 186 ° C. of lithium. The lithium ion secondary battery has been pointed out to be heated and ignited by a short circuit inside the battery. One of the causes is a low melting point of lithium. In this respect, magnesium has a higher melting point than lithium, and therefore has high safety. Magnesium is more abundant on the earth than lithium, which is a rare metal, and is abundant in resources. However, since the conventional magnesium negative electrode has an oxide film as an insulating layer formed on the surface thereof, there is a problem that it is difficult for electricity to flow, the overvoltage becomes large, and the original battery capacity characteristics cannot be exhibited.
　そこで、上記問題を解決するためにいくつかの提案がなされている。例えば、電解質を改良することにより酸化皮膜の形成を抑制する方法として、ＥｔＭｇＢｒ／ＴＨＦを電解液として用いてマグネシウム負極表面の酸化皮膜を除去する方法が提案されている（非特許文献１）。しかし、この方法では、酸化側の電位に対して耐性がなく、電解液の分解が生じるため長期での充放電が行えないとの問題がある。また、使用できる正極材料が限られており、電圧１Ｖ程度の低電位の電池しか報告されていない。負極を改良する方法としては、負極にマグネシウムの金属間化合物を使用する方法が提案され、マグネシウムとビスマスのモル比が３：２に調製された金属間化合物を用いることが提案されている（特許文献１、非特許文献２）。しかしこの方法の場合、マグネシウム－ビスマス金属間化合物は、マグネシウムの含有量が１６質量％程度であるため使用できるマグネシウムの量が少ない。また、金属間化合物は脆いため、そのまま電極として用いると耐久性に問題がある。耐久性を高めるために、バインダーを用いると導電助剤を添加する必要があり、バインダーや導電助剤の重量も加味すると、マグネシウムの含有量は１３％程度と更に少なくなる。そのため、電池あたりにおけるマグネシウムの電気化学的エネルギーへの寄与が小さいとの問題があった。 Therefore, some proposals have been made to solve the above problems. For example, as a method of suppressing the formation of an oxide film by improving the electrolyte, a method of removing the oxide film on the surface of the magnesium negative electrode using EtMgBr / THF as an electrolytic solution has been proposed (Non-Patent Document 1). However, this method has a problem that it is not resistant to the potential on the oxidation side and the electrolytic solution is decomposed, so that charging / discharging for a long time cannot be performed. In addition, the positive electrode materials that can be used are limited, and only low-potential batteries with a voltage of about 1 V have been reported. As a method for improving the negative electrode, a method using an intermetallic compound of magnesium for the negative electrode is proposed, and an intermetallic compound prepared with a molar ratio of magnesium and bismuth of 3: 2 is proposed (patent) Document 1, Non-Patent Document 2). However, in the case of this method, the magnesium-bismuth intermetallic compound has a magnesium content of about 16% by mass, so that the amount of magnesium that can be used is small. In addition, since intermetallic compounds are brittle, there is a problem in durability when used as an electrode as it is. In order to improve durability, when a binder is used, it is necessary to add a conductive additive. When the weight of the binder or conductive additive is taken into consideration, the magnesium content is further reduced to about 13%. Therefore, there has been a problem that the contribution of magnesium to electrochemical energy per battery is small.
特表２０１４－５１２６３７号公報Special table 2014-512737 gazette
　本発明の課題は、上記問題を解決し、酸化皮膜の形成が抑制され、高電位かつ高容量なマグネシウム二次電池を作製できる電極、及び酸化皮膜形成が抑制された高電位かつ高容量なマグネシウム二次電池を提供することにある。 SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, suppress the formation of an oxide film, and produce an electrode capable of producing a high-potential and high-capacity magnesium secondary battery; It is to provide a secondary battery.
　本発明者らは、マグネシウム二次電池における電極上の酸化皮膜の形成を抑制する方法を検討するなかで、マグネシウム二次電池を構成する要素のうちからマグネシウム電極自体に着目し、開発に着手した。マグネシウムを任意の割合でビスマスと合金化し、マグネシウム二次電池の負極としてその電気化学特性を評価したところ、これまでの金属間化合物（Ｍｇ３Ｂｉ２）とは異なり、より少ないビスマス量の合金にて酸化皮膜の形成が抑制され、高電位かつ高容量なマグネシウム二次電池用の電極として使用できることを見いだした。また、これまで報告されているマグネシウム－ビスマス合金電極は、脆い金属間化合物（Ｍｇ３Ｂｉ２）であり電極の成形加工特性に乏しく、電極にするためには導電性カーボン及び結着剤（バインダー）などを用いる必要があり、電極として機能させるためには高容量であるマグネシウムの含有量は著しく減少する（Ｍｇ含有量１３質量％以下）。本発明者らは、合金中の組成をＭｇ－Ｂｉ固溶体又はＭｇ－Ｍｇ３Ｂｉ２共晶の多い状態にすることで、成形加工特性に優れた電極材料となることを見いだした。 While examining the method of suppressing the formation of an oxide film on the electrode in the magnesium secondary battery, the present inventors focused on the magnesium electrode itself from the elements constituting the magnesium secondary battery and started development. . Magnesium was alloyed with bismuth at an arbitrary ratio, and its electrochemical characteristics were evaluated as a negative electrode of a magnesium secondary battery. Unlike conventional intermetallic compounds (Mg 3 Bi 2 ), an alloy with a smaller amount of bismuth was formed. As a result, it was found that the formation of an oxide film is suppressed, and it can be used as an electrode for a magnesium secondary battery having a high potential and a high capacity. In addition, the magnesium-bismuth alloy electrode reported so far is a brittle intermetallic compound (Mg 3 Bi 2 ) and has poor electrode forming characteristics. In order to make an electrode, conductive carbon and a binder (binder) In order to function as an electrode, the content of magnesium having a high capacity is remarkably reduced (Mg content is 13% by mass or less). The present inventors have found that an electrode material having excellent forming characteristics can be obtained by setting the composition in the alloy to a state in which there are many Mg—Bi solid solutions or Mg—Mg 3 Bi 2 eutectics.
　すなわち、本発明は以下に示す事項により特定されるものである。
（１）マグネシウム（Ｍｇ）とビスマス（Ｂｉ）との合金層を備える電極であって、前記合金層が、マグネシウム（Ｍｇ）とビスマス（Ｂｉ）との固溶体（Ｍｇ１－ｘＢｉｘ；ただし、ｘは０．００１～０．０１１２）を含む、又はマグネシウム（Ｍｇ）とビスマス（Ｂｉ）との固溶体（Ｍｇ１－ｘＢｉｘ；ただし、ｘは０．００１～０．０１１２）とマグネシウム（Ｍｇ）とビスマス（Ｂｉ）との金属間化合物（Ｍｇ３Ｂｉ２）を含むことを特徴とする電極。
（２）マグネシウム（Ｍｇ）とビスマス（Ｂｉ）との合金中のビスマスの含有量が、前記合金全体に対して１～５８．９質量％であることを特徴とする上記（１）記載の電極。
（３）負極として上記（１）又は（２）記載の電極を備え、さらに電解質層及び正極を備えることを特徴とするマグネシウム二次電池。 That is, the present invention is specified by the following items.
(1) An electrode comprising an alloy layer of magnesium (Mg) and bismuth (Bi), wherein the alloy layer is a solid solution of magnesium (Mg) and bismuth (Bi) (Mg 1-x Bi x ; x includes 0.001 to 0.0112) or a solid solution of magnesium (Mg) and bismuth (Bi) (Mg 1-x Bi x ; where x is 0.001 to 0.0112) and magnesium (Mg ) And an bismuth (Bi) intermetallic compound (Mg 3 Bi 2 ).
(2) The electrode according to (1), wherein the content of bismuth in the alloy of magnesium (Mg) and bismuth (Bi) is 1 to 58.9% by mass with respect to the whole alloy .
(3) A magnesium secondary battery comprising the electrode according to (1) or (2) as a negative electrode, and further comprising an electrolyte layer and a positive electrode.
　本発明の電極は、酸化皮膜の形成を抑制しつつ、マグネシウムの含有量を多くできる。また、バインダーや導電助剤を必要とせずに電極として使用できる形態に加工できる。本発明のマグネシウム二次電池は、酸化皮膜の形成を抑制できるため、過電圧を抑制し、高電位かつ高容量な二次電池を得ることができる。 The electrode of the present invention can increase the magnesium content while suppressing the formation of an oxide film. Moreover, it can process into the form which can be used as an electrode, without requiring a binder and a conductive support agent. Since the magnesium secondary battery of this invention can suppress formation of an oxide film, it can suppress an overvoltage and can obtain a secondary battery with a high potential and a high capacity.
実施例１におけるビスマス含有量が２質量％のマグネシウム－ビスマス合金のサイクリックボルタンメトリーを示す図である。FIG. 3 is a diagram showing cyclic voltammetry of a magnesium-bismuth alloy having a bismuth content of 2 mass% in Example 1. 実施例１におけるビスマス含有量が３０質量％のマグネシウム－ビスマス合金のサイクリックボルタンメトリーを示す図である。FIG. 3 is a view showing cyclic voltammetry of a magnesium-bismuth alloy having a bismuth content of 30% by mass in Example 1. 実施例１におけるビスマス含有量が５０質量％のマグネシウム－ビスマス合金のサイクリックボルタンメトリーを示す図である。FIG. 3 is a diagram showing cyclic voltammetry of a magnesium-bismuth alloy having a bismuth content of 50% by mass in Example 1. 比較例１におけるビスマス含有量が０質量％のマグネシウムのサイクリックボルタンメトリーを示す図である。It is a figure which shows the cyclic voltammetry of magnesium whose bismuth content in the comparative example 1 is 0 mass%. 実施例２で作製したマグネシウム二次電池の構成を示す図である。6 is a diagram showing a configuration of a magnesium secondary battery produced in Example 2. FIG. 実施例２で作製したマグネシウム二次電池の充放電測定の結果を示す図である。6 is a diagram showing the results of charge / discharge measurement of a magnesium secondary battery produced in Example 2. FIG. 比較例２で作製したマグネシウム二次電池の充放電測定の結果を示す図である。6 is a diagram showing the results of charge / discharge measurement of a magnesium secondary battery produced in Comparative Example 2. FIG.
　本発明の電極は、マグネシウムとビスマスの合金層を備える電極であって、前記合金が、マグネシウムとビスマスの固溶体を含む、又はマグネシウムとビスマスの固溶体とマグネシウムとビスマスの金属間化合物を含むことを特徴とする。また、本発明においてマグネシウムとビスマスの固溶体とマグネシウムとビスマスの金属間化合物を含むとは、マグネシウムとビスマスの固溶体と金属間化合物とが共晶の組織形態で合金中に存在する場合も含む。マグネシウム（Ｍｇ）とビスマス（Ｂｉ）の二元系合金は、その状態図から合金におけるＢｉ含有量が固溶限である８．８７質量％（１．１２ａｔ％）までは金属Ｍｇ及びＭｇ－Ｂｉ固溶体を形成し、８．８７質量％（１．１２ａｔ％）から共晶点である５８．９質量％（１４．３ａｔ％）まではＭｇ－Ｂｉ固溶体とＭｇ－Ｍｇ３Ｂｉ２共晶を形成し、５８．９質量％（１４．３ａｔ％）から８２．２質量％（３５ａｔ％）まではＭｇ－Ｍｇ３Ｂｉ２共晶とＭｇ３Ｂｉ２金属間化合物を形成し、８２．２質量％（３５ａｔ％）以上ではＭｇ３Ｂｉ２金属間化合物とＢｉ－Ｍｇ固溶体及び金属Ｂｉを形成することが知られており、製造条件によって組織の形態が異なる。本発明におけるマグネシウムとビスマスの合金（以下、「本発明におけるマグネシウム合金」ともいう。）は、マグネシウムとビスマスの固溶体、又はマグネシウムとビスマスの固溶体とマグネシウムとビスマスの金属間化合物を含む。すなわち、本発明におけるマグネシウム合金の組成は、金属Ｍｇ及びＭｇ－Ｂｉ固溶体が共存する形態、Ｍｇ－Ｂｉ固溶体とＭｇ－Ｍｇ３Ｂｉ２共晶が共存する形態、及びＭｇ－Ｍｇ３Ｂｉ２共晶とＭｇ３Ｂｉ２金属間化合物が共存する形態を含む。本発明におけるマグネシウム合金のビスマスの含有量は、電池反応が金属Ｍｇ及びＭｇ－Ｂｉ固溶体の溶解－析出を伴うため、その体積当たりの電気容量を大きくする観点から、合金中に固溶体が形成されなくなるマグネシウム合金全体に対して５８．９質量％以下が好ましく、５０質量％以下がより好ましい。本発明におけるマグネシウム合金のビスマスの含有量は、マグネシウム合金の加工成形性の観点から、マグネシウム合金全体に対して１～５０質量％であることが好ましい。また、本発明におけるマグネシウム合金のビスマスの含有量は、酸化皮膜形成の抑制効果の観点から、マグネシウム合金全体に対して１～５８．９質量％であることが好ましく、１～５０質量％であることがより好ましく、３０～５０質量％であることがさらに好ましい。本発明におけるマグネシウムとビスマスの固溶体（Ｍｇ１－ｘＢｉｘ）では、ｘは固溶体として実質的に存在できる下限である０．００１以上、固溶限である０．０１１２以下の範囲が好ましい。本発明の電極における合金層は、マグネシウム（Ｍｇ）とビスマス（Ｂｉ）との固溶体（Ｍｇ１－ｘＢｉｘ；ただし、ｘは０．００１～０．０１１２）を含む、又はマグネシウム（Ｍｇ）とビスマス（Ｂｉ）との固溶体（Ｍｇ１－ｘＢｉｘ；ただし、ｘは０．００１～０．０１１２）とマグネシウム（Ｍｇ）とビスマス（Ｂｉ）との金属間化合物（Ｍｇ３Ｂｉ２）を含む。 The electrode of the present invention is an electrode having an alloy layer of magnesium and bismuth, wherein the alloy contains a solid solution of magnesium and bismuth, or contains a solid solution of magnesium and bismuth and an intermetallic compound of magnesium and bismuth. And Further, in the present invention, the phrase “containing a solid solution of magnesium and bismuth and an intermetallic compound of magnesium and bismuth” includes the case where the solid solution of magnesium and bismuth and the intermetallic compound are present in the alloy in the form of a eutectic structure. In the binary alloy of magnesium (Mg) and bismuth (Bi), metal Mg and Mg—Bi are used until the Bi content of the alloy is 8.87 mass% (1.12 at%), which is the solid solubility limit. Solid solution is formed, and Mg—Bi solid solution and Mg—Mg 3 Bi 2 eutectic are formed from 8.87 mass% (1.12 at%) to the eutectic point of 58.9 mass% (14.3 at%). From 58.9 mass% (14.3 at%) to 82.2 mass% (35 at%), an Mg—Mg 3 Bi 2 eutectic and an Mg 3 Bi 2 intermetallic compound are formed, and 82.2 mass% (35 at%) or more is known to form a Mg 3 Bi 2 intermetallic compound, a Bi—Mg solid solution, and metal Bi, and the form of the structure varies depending on the production conditions. The alloy of magnesium and bismuth in the present invention (hereinafter also referred to as “magnesium alloy in the present invention”) includes a solid solution of magnesium and bismuth, or a solid solution of magnesium and bismuth and an intermetallic compound of magnesium and bismuth. That is, the composition of the magnesium alloy in the present invention includes the form in which the metallic Mg and Mg—Bi solid solution coexist, the form in which the Mg—Bi solid solution and Mg—Mg 3 Bi 2 eutectic coexist, and the Mg—Mg 3 Bi 2 eutectic. And Mg 3 Bi 2 intermetallic compound are included. The content of bismuth in the magnesium alloy in the present invention is such that the battery reaction involves dissolution-precipitation of the metal Mg and Mg—Bi solid solution, so that no solid solution is formed in the alloy from the viewpoint of increasing the electric capacity per volume. 58.9 mass% or less is preferable with respect to the whole magnesium alloy, and 50 mass% or less is more preferable. In the present invention, the bismuth content of the magnesium alloy is preferably 1 to 50% by mass with respect to the entire magnesium alloy from the viewpoint of workability of the magnesium alloy. In addition, the bismuth content of the magnesium alloy in the present invention is preferably 1 to 58.9% by mass, and preferably 1 to 50% by mass, based on the entire magnesium alloy, from the viewpoint of the effect of suppressing the formation of an oxide film. More preferably, the content is 30 to 50% by mass. In the solid solution of magnesium and bismuth (Mg 1-x Bi x ) in the present invention, x is preferably in the range of 0.001 or more which is the lower limit that can substantially exist as a solid solution and 0.0112 or less which is the solid solution limit. The alloy layer in the electrode of the present invention contains a solid solution of Mg (Mg) and bismuth (Bi) (Mg 1-x Bi x ; where x is 0.001 to 0.0112), or magnesium (Mg) and Includes a solid solution with bismuth (Bi) (Mg 1-x Bi x ; x is 0.001 to 0.0112), an intermetallic compound (Mg 3 Bi 2 ) of magnesium (Mg) and bismuth (Bi) .
　本発明におけるマグネシウム合金は、充分な強度を有し、板状、柱状等の形態に容易に加工できるため、加工した形態のマグネシウム合金そのものを電極として使用する、あるいは集電体に取り付けて電極として使用することができる。そのため、粒状の電極材料を使用する場合のように、バインダーや導電助剤を必要とすることなく電極を作製できるので、電極におけるマグネシウムの含有量を減少させずに電極を作製できる。また、マグネシウム合金を鱗片形状、偏平形状、紡錘形状、球状等の粒状に加工し、バインダーと混合して集電体上に固定する等の方法により電極を作製してもよい。本発明における「マグネシウム合金層」とは、本発明におけるマグネシウム合金を含む層の意味であり、本発明におけるマグネシウム合金が、板状、柱状等の形態に加工されマグネシウム合金そのものがマグネシウム合金層を形成している場合、及びマグネシウム合金の粒子がバインダー等で固定されマグネシウム合金層を形成している場合を含む。本発明における「マグネシウム合金層を備える電極」とは、電極が上記マグネシウム合金層を有していればよく、マグネシウム合金層のみで電極を構成している場合、マグネシウム合金層と集電体等の他の構成部品と共に電極が構成されている場合を含む。 Since the magnesium alloy in the present invention has sufficient strength and can be easily processed into a plate shape, a columnar shape, etc., the processed form of the magnesium alloy itself is used as an electrode or attached to a current collector as an electrode. Can be used. Therefore, as in the case of using a granular electrode material, the electrode can be produced without the need for a binder or a conductive additive, and therefore the electrode can be produced without reducing the magnesium content in the electrode. Alternatively, the electrode may be produced by processing the magnesium alloy into a scale shape, a flat shape, a spindle shape, a spherical shape, or the like, mixing with a binder, and fixing on the current collector. The “magnesium alloy layer” in the present invention means a layer containing a magnesium alloy in the present invention, and the magnesium alloy in the present invention is processed into a plate shape, a columnar shape, etc., and the magnesium alloy itself forms a magnesium alloy layer. And the case where the magnesium alloy particles are fixed with a binder or the like to form a magnesium alloy layer. The “electrode having a magnesium alloy layer” in the present invention is only required that the electrode has the magnesium alloy layer, and when the electrode is composed of only the magnesium alloy layer, the magnesium alloy layer and the current collector, etc. This includes the case where the electrode is configured together with other components.
　本発明の電池は、本発明の電極を負極として備え、さらに電解質層及び正極を備えることを特徴とする。本発明の電池における正極、電解質、及び必要に応じて他の構成要素は、従来のマグネシウム二次電池に使用されているものを使用することができる。例えば、正極としては、正極活物質がバインダーにより集電体上に固定されたものを挙げることができ、必要に応じて導電助剤を含んでもよい。正極活物質としては、例えば、硫黄又は硫黄化合物、Ｖ２Ｏ５、硫黄ドープＶ２Ｏ５等のＶ２Ｏ５系、ＭｎＯ２系、ＭｎＯ３、ＭｇＭｎＯ３等のＭｎＯ３系などの酸化物系の正極、Ｍｏ６Ｓ８系等の硫化物系の正極、Ｍｇ１．０３Ｍｎ０．９７ＳｉＯ４、ＭｇＣｏＳｉＯ４、ＭｇＦｅＳｉＯ４、ＭｇＭｎＳｉＯ４、Ｍｏ９Ｓｅ１１、ＦｅＰＯ４などを挙げることができる。バインダーとしては、例えば、ポリフッ化ビニリデン、ポリテトラフルオロエチレン等のフッ素含有樹脂、スチレンブタジエンゴム、カルボキシメチルセルロース等の樹脂材料などを挙げることができる。また、導電助剤としては、例えば、無定型炭素、天然黒鉛、人造黒鉛等の黒鉛、アセチレンブラック、ケッチェンブラック、チャンネルブラック、ファーネスブラック、ランプブラック、サーマルブラック等のカーボンブラック、カーボンナノチューブ等の炭素質物質などを挙げることができる。 The battery of the present invention includes the electrode of the present invention as a negative electrode, and further includes an electrolyte layer and a positive electrode. What is used for the conventional magnesium secondary battery can be used for the positive electrode in the battery of this invention, electrolyte, and another component as needed. For example, examples of the positive electrode include those in which a positive electrode active material is fixed on a current collector by a binder, and may include a conductive aid as necessary. As the positive electrode active material, for example, sulfur or sulfur compounds, V 2 O 5, sulfur-doped V 2 O 5 or the like V 2 O 5 system, MnO 2 system, MnO 3, MgMnO oxides such as MnO 3 system, such as 3 Positive electrode of sulfide type, positive electrode of sulfide type such as Mo 6 S 8 type, Mg 1.03 Mn 0.97 SiO 4 , MgCoSiO 4 , MgFeSiO 4 , MgMnSiO 4, Mo 9 Se 11 , FePO 4 and the like. . Examples of the binder include fluorine-containing resins such as polyvinylidene fluoride and polytetrafluoroethylene, and resin materials such as styrene butadiene rubber and carboxymethyl cellulose. Examples of the conductive assistant include graphite such as amorphous carbon, natural graphite, and artificial graphite, carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black, and carbon nanotube. Examples include carbonaceous materials.
　電解質としては、例えば、過塩素酸マグネシウム（Ｍｇ（ＣｌＯ４）２）、グリニャール試薬（ＲＭｇＸ（Ｒは有機基、Ｘはハロゲンである。））、臭化マグネシウム（ＭｇＢｒ2）等のハロゲン化マグネシウム、硝酸マグネシウム（Ｍｇ（ＮＯ3）2）、マグネシウムビストリフルオロメタンスルホンイミド（Ｍｇ（ＴＦＳＩ）２）、Ｍｇ（ＳＯ２ＣＦ３）２、ホウフッ化マグネシウム（Ｍｇ（ＢＦ４）２）、トリフルオロメチルスルホン酸マグネシウム（Ｍｇ（ＣＦ３ＳＯ３）２）、ヘキサフルオロ燐酸マグネシウム（Ｍｇ（ＰＦ６）２）などを挙げることができる。電解質溶媒としては、公知の非水電解質溶媒を用いることができ、例えば、アセトニトリル（ＡＮ）、ジエトキエタン、ジエチレングリコールジメチルエーテル(ジグライム)、トリエチレングリコールジメチルエーテル（トリグライム）、テトラグライムジメチルエーテル(テトラグライム)、テトラヒドロフラン（ＴＨＦ）、プロピレンカーボネート（ＰＣ）、エチレンカーボネート、ブチレンカーボネート、ビニレンカーボネート、γ－ブチルラクトン、スルホラン、１，２－ジメトキシエタン、１，２－ジエトキシエタン、２－メチルテトラヒドロフラン、３－メチル－１，３－ジオキソラン、プロピオン酸メチル、酪酸メチル、ジメチルカーボネート、ジエチルカーボネート、ジプロピルカーボネート等を挙げることができる。 Examples of the electrolyte include magnesium halides such as magnesium perchlorate (Mg (ClO 4 ) 2 ), Grignard reagent (RMgX (R is an organic group, X is a halogen)), magnesium bromide (MgBr 2 ), and the like. , Magnesium nitrate (Mg (NO 3 ) 2 ), magnesium bistrifluoromethanesulfonimide (Mg (TFSI) 2 ), Mg (SO 2 CF 3 ) 2 , magnesium borofluoride (Mg (BF 4 ) 2 ), trifluoromethyl Examples thereof include magnesium sulfonate (Mg (CF 3 SO 3 ) 2 ), magnesium hexafluorophosphate (Mg (PF 6 ) 2 ), and the like. As the electrolyte solvent, known non-aqueous electrolyte solvents can be used. For example, acetonitrile (AN), dietochiethane, diethylene glycol dimethyl ether (diglyme), triethylene glycol dimethyl ether (triglyme), tetraglyme dimethyl ether (tetraglyme), tetrahydrofuran ( THF), propylene carbonate (PC), ethylene carbonate, butylene carbonate, vinylene carbonate, γ-butyllactone, sulfolane, 1,2-dimethoxyethane, 1,2-diethoxyethane, 2-methyltetrahydrofuran, 3-methyl-1 , 3-dioxolane, methyl propionate, methyl butyrate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate and the like.
［実施例１］
　（電極の前処理）
ビスマス（Ｂｉ）の含有量が２質量％、３０質量％、５０質量％である本発明におけるマグネシウム－ビスマス合金（Ｍｇ－Ｂｉ合金）を、直径７ｍｍ、厚さ２ｍｍの円柱状に切り出し、それぞれの金属片の両面をエメリーペーパー♯２２０、６００、２０００の順番で研磨して、試験片とした。 [Example 1]
(Pretreatment of electrodes)
A magnesium-bismuth alloy (Mg-Bi alloy) according to the present invention having a bismuth (Bi) content of 2% by mass, 30% by mass, and 50% by mass is cut into a cylindrical shape having a diameter of 7 mm and a thickness of 2 mm. Both surfaces of the metal piece were polished in the order of emery paper # 220, 600, 2000 to obtain a test piece.
　（サイクリックボルタンメトリー）
各試験片を試験極とし、参照極をＡｇ線（株式会社ニコラ製、純度９９．９９％）、対極をマグネシウムリボン（株式会社ニコラ製、純度９９．９９％）として、三極式ビーカーセルを用いて、サイクリックボルタンメトリーを行った。電解液は、０．５Ｍ マグネシウムビストリフルオロメタンスルホンイミド［Ｍｇ（ＴＦＳＡ）２］／トリグライムを用いた。走査範囲は、－３．５～１．０Ｖとし、走査速度は１０ｍＶ／ｓに統一して、５サイクルを行った。ビスマスの含有量がそれぞれ２質量％、３０質量％、５０質量％であるＭｇ－Ｂｉ合金の結果を図１～図３に示す。図中、点線１は１サイクル目の結果であり、破線５は５サイクル目の結果である。 (Cyclic voltammetry)
Each test piece is a test electrode, a reference electrode is an Ag wire (Nicola Co., Ltd., purity 99.99%), and a counter electrode is a magnesium ribbon (Nicola Co., Ltd., purity 99.99%). Used to perform cyclic voltammetry. As the electrolytic solution, 0.5M magnesium bistrifluoromethanesulfonimide [Mg (TFSA) 2 ] / triglyme was used. The scanning range was −3.5 to 1.0 V, the scanning speed was unified to 10 mV / s, and 5 cycles were performed. The results of Mg—Bi alloys having bismuth contents of 2% by mass, 30% by mass and 50% by mass are shown in FIGS. In the figure, dotted line 1 is the result of the first cycle, and broken line 5 is the result of the fifth cycle.
　［比較例１］
ビスマスを含有しないマグネシウム金属を、直径７ｍｍ、厚さ２ｍｍの円柱状に切り出し、実施例と同様に金属片を作成、処理して試験片を作製した。作製した試験片を用いて実施例と同様にサイクリックボルタンメトリーを行った。結果を図４に示す。 [Comparative Example 1]
Magnesium metal not containing bismuth was cut into a cylindrical shape having a diameter of 7 mm and a thickness of 2 mm, and a metal piece was prepared and processed in the same manner as in the example to prepare a test piece. Cyclic voltammetry was performed in the same manner as in the example using the prepared test piece. The results are shown in FIG.
　図４に示されるように、比較例のマグネシウム試験片を用いた場合、マグネシウムの溶解－析出に起因する酸化－還元応答の立ち上がりの電位差は２Ｖ以上ある。これはマグネシウム電極表面に形成される酸化皮膜による影響である。一方、実施例のＭｇ－Ｂｉ合金を試験片に用いた場合、図１～３に示されるように、酸化－還元応答の立ち上がりの電位差は小さく、特にＢｉ含有量が３０質量％以上になると電位差なく酸化－還元応答が観察されている。このように、実施例のＭｇ－Ｂｉ合金では、酸化皮膜の形成が抑制されたことがわかる。これにより、より高い電位からの充放電が可能となり、高容量なマグネシウム二次電池の提供が可能となる。また、実施例のＭｇ－Ｂｉ合金のマグネシウム含有量は、９８～５０質量％であり、例えば、Ｍｇ３Ｂｉ２金属間化合物におけるマグネシウム含有量の１６質量％に比べて、極めて多い。 As shown in FIG. 4, when the magnesium test piece of the comparative example is used, the potential difference at the rise of the oxidation-reduction response due to dissolution-precipitation of magnesium is 2 V or more. This is an effect of the oxide film formed on the surface of the magnesium electrode. On the other hand, when the Mg—Bi alloy of the example is used as a test piece, as shown in FIGS. 1 to 3, the potential difference at the start of the oxidation-reduction response is small, particularly when the Bi content is 30% by mass or more. An oxidation-reduction response has been observed. Thus, it can be seen that the formation of the oxide film was suppressed in the Mg—Bi alloy of the example. Thereby, charging / discharging from a higher potential is possible, and a high-capacity magnesium secondary battery can be provided. In addition, the magnesium content of the Mg—Bi alloy of the example is 98 to 50% by mass, and is extremely large, for example, compared to 16% by mass of the magnesium content in the Mg 3 Bi 2 intermetallic compound.
［実施例２］
（正極活物質の合成）
硫黄（Ｓ８）と式（Ｉ）で表されるクラウンエーテル化合物とのモル比が１：０．５となるように、硫黄（Ｓ８）（０．５ｇ、１．９５ｍｍｏｌ）を反応容器に入れ、１５５℃で１０分間攪拌した。硫黄が溶解した後に、前記クラウンエーテル化合物（０．８２０ｇ、０．９８ｍｍｏｌ）を加え、１６０～１６５℃に加熱し攪拌した。当初、液状の反応混合物は、２０分程度で固まるが、そのまま反応を続け、６０分間、約１６０℃で加熱反応を行う。さらに、１７０℃に加熱し撹拌することで、黄褐色ゴム状の含硫黄ポリマーを定量的に得た。
Figure JPOXMLDOC01-appb-C000001
 [Example 2]
(Synthesis of positive electrode active material)
The molar ratio of the crown ether compound represented by the sulfur (S 8) and formula (I) is 1: to 0.5, sulfur (S 8) (0.5g, 1.95mmol ) in a reaction vessel The mixture was stirred at 155 ° C. for 10 minutes. After the sulfur was dissolved, the crown ether compound (0.820 g, 0.98 mmol) was added, and the mixture was heated to 160 to 165 ° C. and stirred. Initially, the liquid reaction mixture hardens in about 20 minutes, but the reaction is continued as it is, and a heating reaction is performed at about 160 ° C. for 60 minutes. Furthermore, a yellowish brown rubber-like sulfur-containing polymer was quantitatively obtained by heating to 170 ° C. and stirring.
Figure JPOXMLDOC01-appb-C000001
（正極の作製）
合成した含硫黄ポリマーとケッチェンブラックとポリテトラフッ化エチレンを重量比３：６：１の割合で乾式法により混合し、その混合物を集電体（ＳＵＳ）に圧着させることにより正極を作製した。 (Preparation of positive electrode)
The synthesized sulfur-containing polymer, ketjen black and polytetrafluoroethylene were mixed at a weight ratio of 3: 6: 1 by a dry method, and the mixture was pressure-bonded to a current collector (SUS) to produce a positive electrode.
（マグネシウム二次電池の作成及び評価）
上記で作製した正極、電解質としてＭｇ（ＴＦＳＡ）２／トリエチレングリコールジメチルエーテル（Ｔｒｉｇｌｙｍｅ）を含侵させたセパレータ、及び負極に本発明におけるマグネシウム-ビスマス合金(ビスマス５０ｗｔ％含有)板を用いて、図５に示されるように配置してマグネシウム二次電池を作製し、室温にて充放電測定を行った。充放電測定の結果を図６に示す。 (Production and evaluation of magnesium secondary battery)
Using the positive electrode produced above, a separator impregnated with Mg (TFSA) 2 / triethylene glycol dimethyl ether (Triglyme) as an electrolyte, and a magnesium-bismuth alloy (containing bismuth 50 wt%) plate according to the present invention for the negative electrode, As shown in FIG. 5, a magnesium secondary battery was prepared, and charge / discharge measurement was performed at room temperature. The result of the charge / discharge measurement is shown in FIG.
［比較例２］
上記で作製した正極、電解質としてＭｇ（ＴＦＳＡ）２／トリエチレングリコールジメチルエーテル（Ｔｒｉｇｌｙｍｅ）を含侵させたセパレータ、及び負極にマグネシウム板を用いて、図５に示されるように配置してマグネシウム二次電池を作製し、室温にて充放電測定を行った。充放電測定の結果を図７に示す。 [Comparative Example 2]
Using the positive electrode prepared above, a separator impregnated with Mg (TFSA) 2 / triethylene glycol dimethyl ether (Triglyme) as an electrolyte, and a magnesium plate for the negative electrode, the magnesium secondary is arranged as shown in FIG. A battery was prepared, and charge / discharge measurement was performed at room temperature. The result of the charge / discharge measurement is shown in FIG.
本発明におけるＭｇ－Ｂｉ合金を負極として用いて、マグネシウム－硫黄電池の充放電測定を行った結果、通常の純マグネシウム金属の負極と比較して、高電位の放電挙動が得られたことより、負極でのマグネシウムの酸化被膜の抑制効果が確認された。それに伴い、放電容量もほぼ硫黄の理論容量に達した。 Using the Mg—Bi alloy in the present invention as a negative electrode, the results of charge / discharge measurement of a magnesium-sulfur battery showed that a high-potential discharge behavior was obtained as compared with a normal pure magnesium metal negative electrode. The suppression effect of the magnesium oxide film in the negative electrode was confirmed. Along with this, the discharge capacity also reached the theoretical capacity of sulfur.
　本発明の電極は、電極表面への酸化皮膜の形成が抑制され、マグネシウムの含有量が多いので、マグネシウム二次電池に好適に用いることができ、過電圧を抑制し、高電位かつ高容量な二次電池を得ることができる。また、本発明の電極は、マグネシウム合金を電極材料として使用しているため、電極として充分な強度と耐久性を有する。本発明のマグネシウム二次電池は、電極上への酸化皮膜の形成が抑制されるので、マグネシウムが有する電気特性を充分に発揮することができ、高電位かつ高容量な二次電池を得ることができる。そのため、本発明のマグネシウム二次電池は、車載用途や大型用途に対して好適である。 Since the electrode of the present invention suppresses the formation of an oxide film on the electrode surface and has a high magnesium content, it can be suitably used for a magnesium secondary battery, suppresses overvoltage, and has a high potential and high capacity. A secondary battery can be obtained. Moreover, since the electrode of this invention uses a magnesium alloy as an electrode material, it has sufficient intensity | strength and durability as an electrode. In the magnesium secondary battery of the present invention, formation of an oxide film on the electrode is suppressed, so that the electrical characteristics possessed by magnesium can be sufficiently exhibited, and a high-potential and high-capacity secondary battery can be obtained. it can. Therefore, the magnesium secondary battery of the present invention is suitable for in-vehicle applications and large applications.

Claims (3)

  1. マグネシウム（Ｍｇ）とビスマス（Ｂｉ）との合金層を備える電極であって、前記合金層が、マグネシウム（Ｍｇ）とビスマス（Ｂｉ）との固溶体（Ｍｇ１－ｘＢｉｘ；ただし、ｘは０．００１～０．０１１２）を含む、又はマグネシウム（Ｍｇ）とビスマス（Ｂｉ）との固溶体（Ｍｇ１－ｘＢｉｘ；ただし、ｘは０．００１～０．０１１２）とマグネシウム（Ｍｇ）とビスマス（Ｂｉ）との金属間化合物（Ｍｇ３Ｂｉ２）を含むことを特徴とする電極。 An electrode comprising an alloy layer of magnesium (Mg) and bismuth (Bi), wherein the alloy layer is a solid solution of Mg (Mg) and bismuth (Bi) (Mg 1-x Bi x ; where x is 0 .001 to 0.0112) or a solid solution of magnesium (Mg) and bismuth (Bi) (Mg 1-x Bi x ; where x is 0.001 to 0.0112), magnesium (Mg) and bismuth An electrode comprising an intermetallic compound (Mg 3 Bi 2 ) with (Bi).
  2. マグネシウム（Ｍｇ）とビスマス（Ｂｉ）との合金中のビスマスの含有量が、前記合金全体に対して１～５８．９質量％であることを特徴とする請求項１記載の電極。 The electrode according to claim 1, wherein the content of bismuth in the alloy of magnesium (Mg) and bismuth (Bi) is 1 to 58.9 mass% with respect to the whole alloy.
  3. 負極として請求項１又は２記載の電極を備え、さらに電解質層及び正極を備えることを特徴とするマグネシウム二次電池。 A magnesium secondary battery comprising the electrode according to claim 1 or 2 as a negative electrode, and further comprising an electrolyte layer and a positive electrode.
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