Electrochemical device

Abstract

This electrochemical device comprises: a negative electrode that includes a magnesium-containing material; and an electrolyte solution that includes lithium ions, magnesium ions, trifluoromethanesulfonic acid ions (TFO ions), and bis(trifluoromethanesulfonyl)imide ions (TFSI ions).

Description

Electrochemical Devices

[0001] The present invention relates to an electrochemical device.

[0002] Patent Document 1 and Non-Patent Documents 1 and 2 describe a secondary battery (magnesium secondary battery in Patent Document 1) that uses a magnesium-containing material as the negative electrode. Known electrolytes for magnesium secondary batteries include electrolytes containing magnesium ions and TSI ions (bis(trifluoromethanesulfonyl)imide ions) (see, for example, Patent Document 1 and Non-Patent Document 2) and electrolytes containing magnesium ions and TFO ions (trifluoromethanesulfonate ions) (see Non-Patent Document 1).

[0003] International Publication No. 2020 / 090946

[0004] Cell Rep. Phys. Sci. 2020, 1, 100265J. Electrochem. Soc. 2015, 162, A7118

[0005] There is a demand for improved coulombic efficiency in secondary batteries (electrochemical devices) that use magnesium-containing materials as negative electrodes.

[0006] An object of the present invention is to provide an electrochemical device that can improve the coulomb efficiency.

[0007] An electrochemical device according to one embodiment includes a negative electrode including a magnesium-containing material and an electrolyte solution including lithium ions, magnesium ions, TFO ions (trifluoromethanesulfonate ions), and TFSI ions (bis(trifluoromethanesulfonyl)imide ions).

[0008] According to the electrochemical device of the present invention, the coulomb efficiency can be improved.

[0009] FIG. 1 is a cross-sectional view schematically showing the configuration of a secondary battery according to an embodiment. FIG. 2 is an explanatory diagram for explaining the configuration of a secondary battery (coin cell) according to Example 1. FIG. 3 is a graph showing charge / discharge curves of the secondary battery according to Example 1. FIG. 4 is a graph showing charge / discharge curves of the secondary battery according to Comparative Example 1. FIG. 5 is a graph showing charge / discharge curves of the secondary battery according to Example 2. FIG. 6 is a graph showing charge / discharge curves of the secondary battery according to Comparative Example 2.

[0010] Hereinafter, embodiments of the present disclosure will be described, but the present disclosure is not limited to these embodiments.

[0011] (Embodiment) Fig. 1 is a cross-sectional view schematically showing the configuration of a secondary battery according to an embodiment. As shown in Fig. 1, the secondary battery 1 according to the embodiment has a positive electrode 10, a negative electrode 20, a separator 30, and an electrolyte (not shown). The positive electrode 10 and the negative electrode 20 are stacked with the separator 30 interposed therebetween. The secondary battery 1 according to the embodiment is a magnesium secondary battery in which a magnesium-containing material is used as the negative electrode 20.

[0012] The positive electrode 10 includes a positive electrode current collector and a positive electrode active material layer (not shown). However, the positive electrode current collector may be omitted.

[0013] The positive electrode current collector is a conductive support that supports the positive electrode active material layer and contains a conductive material such as nickel. The positive electrode active material layer is provided on the positive electrode current collector and contains one or more positive electrode active materials that absorb and release magnesium ions. However, the positive electrode active material layer may further contain one or more other materials such as a positive electrode binder and a positive electrode conductive agent.

[0014] The type of the positive electrode active material is not particularly limited, but specific examples include sulfur, graphite fluoride, metal oxides, metal halides, etc. Each of the metal oxides and metal halides contains one or more metal elements selected from the group consisting of scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, and zinc as constituent elements.

[0015] The positive electrode binder contains one or more resin materials such as fluorine-based resins, polyvinyl alcohol-based resins, and styrene-butadiene copolymer rubber. Specific examples of fluorine-based resins include polyvinylidene fluoride and polytetrafluoroethylene. The positive electrode binder may also be a conductive polymer compound. Specific examples of the conductive polymer compound include polyaniline, polypyrrole, and polythiophene, and may also be copolymers of two or more of these. The conductive polymer compound may be unsubstituted or substituted with any one or more functional groups.

[0016] The positive electrode conductive agent contains one or more types of carbon materials. Specific examples of carbon materials include graphite, carbon fiber, carbon black, and carbon nanotubes. Carbon fiber includes vapor-grown carbon fiber (VGCF). Carbon black includes acetylene black and ketjen black. Carbon nanotubes include single-walled carbon nanotubes (SWCNT) and multi-walled carbon nanotubes (MWCNT). Multi-walled carbon nanotubes include double-walled carbon nanotubes (DWCNT). However, the positive electrode conductive agent may be a metal material, a conductive polymer compound, or the like, in addition to a carbon material. A specific example of a metal material is nickel.

[0017] The thickness of the positive electrode active material layer is 5 μm or more. The positive electrode active material layer is provided on one or both surfaces of the positive electrode current collector.

[0018] The negative electrode 20 faces the positive electrode 10 via the separator 30. The negative electrode 20 includes a negative electrode current collector and a negative electrode active material layer (not shown). However, the negative electrode current collector may be omitted.

[0019] The negative electrode current collector is a conductive support that supports the negative electrode active material layer and contains a conductive material such as copper. The negative electrode active material layer is provided on the negative electrode current collector and contains one or more magnesium-based materials. However, the negative electrode active material layer may further contain one or more other materials such as a negative electrode binder and a negative electrode conductive agent.

[0020] Magnesium-based materials (magnesium-containing materials) are a general term for materials that contain magnesium as a constituent element. That is, magnesium-based materials may be magnesium (pure magnesium metal), magnesium alloys, magnesium compounds, or mixtures of two or more of these. The purity of magnesium is not particularly limited, and magnesium may contain any amount of impurities. The types of metal elements (excluding magnesium) contained as constituent elements in magnesium alloys are not particularly limited. Magnesium compounds contain one or more non-metallic elements, such as carbon, oxygen, sulfur, and halogens, as constituent elements. Specific examples of halogens include fluorine, chlorine, bromine, and iodine.

[0021] The negative electrode active material layer contains, in addition to magnesium, for example, lithium, aluminum, and zinc, and the composition ratio of each material constituting the negative electrode active material layer is, for example, 90 wt % or more of magnesium metal, 10 wt % or less of lithium, 10 wt % or less of aluminum, and 2 wt % or less of zinc.

[0022] The negative electrode active material layer made of a magnesium-based material has a thickness of 5 μm or more. The negative electrode active material layer is provided on one side of the negative electrode current collector. Alternatively, the negative electrode active material layer may be provided on both sides of the negative electrode current collector.

[0023] The secondary battery 1 can have an improved energy density by having such a negative electrode 20. Specific examples of the characteristics of the secondary battery 1 will be described later in Examples 1 to 3.

[0024] The separator 30 is an insulating porous film interposed between the positive electrode 10 and the negative electrode 20, and allows magnesium ions and lithium ions to pass through while preventing contact (short circuit) between the positive electrode 10 and the negative electrode 20. The separator 30 contains a polymer compound such as polyethylene.

[0025] The electrolytic solution is a liquid electrolyte impregnated in the separator 30, and contains a solvent, an electrolyte salt, and an additive.

[0026] The solvent is a material that dissolves or disperses the electrolyte salt, and is one or more kinds of organic solvents.

[0027] The type of solvent is not particularly limited, but it is preferable that the solvent contains an ether compound, because the electrolyte salt is easily dissolved or dispersed in the ether compound.

[0028] An ether compound is a general term for compounds having an ether bond (—O—), and may be a chain compound or a cyclic compound. Specific examples of ether compounds include dimethoxyethane, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and tetrahydrofuran. The use of an ether compound facilitates stable dissolution or dispersion of electrolyte salts. Specific examples of the series of ether compounds described here are primarily so-called glyme-based ethers.

[0029] The electrolyte salt is a substance that ionizes in a solvent, and examples of the electrolyte salt include magnesium salts. Examples of the magnesium salt include magnesium bistrifluoromethanesulfonylimide (Mg(TFSI) ２ )

[0030] The electrolyte solution contains an additive other than the electrolyte salt. The additive is a substance that ionizes in a solvent, such as a lithium salt. An example of the lithium salt is lithium trifluoromethanesulfonate (LiTFO).

[0031] The electrolyte solution of this embodiment contains lithium ions, magnesium ions, TFO ions (trifluoromethanesulfonate ions), and TFSI ions (bis(trifluoromethanesulfonyl)imide ions).

[0032] The secondary battery 1 may further include one or more other components, such as an exterior member, a positive electrode lead, and a negative electrode lead.

[0033] The exterior member is a member that houses the positive electrode 10, the negative electrode 20, the separator 30, etc. The type of exterior member is not particularly limited as long as it is a member that can house the positive electrode 10, the negative electrode 20, the separator 30, etc. That is, the exterior member may be a rigid can or a flexible or pliable film.

[0034] 1, detailed illustration is omitted for the sake of simplicity, but the positive electrode 10, the negative electrode 20, and the separator 30 may form a wound structure or a stacked structure. In the wound structure, the positive electrode 10 and the negative electrode 20 are wound while facing each other with the separator 30 interposed therebetween. In the stacked structure, the positive electrode 10 and the negative electrode 20 are alternately stacked with the separator 30 interposed therebetween.

[0035] As described above, in the secondary battery 1 of this embodiment, a magnesium-containing material is used as the negative electrode 20, and the electrolyte contains magnesium ions and TFSI ions (bis(trifluoromethanesulfonyl)imide ions), as well as lithium ions and TFO ions (trifluoromethanesulfonate ions). This activates the surface of the magnesium metal compared to when the electrolyte does not contain lithium ions and TFO ions. As a result, the ionic conductivity of the electrolyte in the secondary battery 1 is improved, and the Coulombic efficiency of the magnesium precipitation and dissolution reaction can be improved.

[0036] Example 1 FIG. 2 is an explanatory diagram illustrating the configuration of a secondary battery (coin cell) according to Example 1. FIG. 3 is a graph showing charge / discharge curves of the secondary battery according to Example 1. FIG. 4 is a graph showing charge / discharge curves of the secondary battery according to Comparative Example 1. Table 1 shows the molar concentrations and coulombic efficiencies of the electrolyte solutions according to Example 1 and Comparative Example 1. Note that the present invention is not limited by the following examples. Note that in the following description of the examples, FIGS. 3 to 6 are drawings showing some of the measured data.

[0037] FIG. 2 is a schematic exploded view of a secondary battery 50 according to Example 1. As shown in FIG. 2, the secondary battery 50 according to Example 1 includes an electrode (hereinafter referred to as a counter electrode) 51 serving as a counter electrode and a reference electrode, a working electrode 52, a separator 53, an anode cup 54, a cathode cup 55, and an electrolyte (not shown). The working electrode 52 and the counter electrode 51 are stacked with the separator 53 interposed therebetween. The stacked working electrode 52, the counter electrode 51, and the separator 53 are sealed inside the anode cup 54 and the cathode cup 55. The working electrode 52, the counter electrode 51, and the separator 53 are each impregnated with an electrolyte. Note that the counter electrode (reference electrode) in this specification corresponds to the negative electrode in the claims, and the working electrode in this specification corresponds to the positive electrode in the claims.

[0038] First, the preparation of the electrolyte solution according to Example 1 will be described. As the magnesium salt, anhydrous magnesium chloride (MgCl) manufactured by Sigma-Aldrich was used. ２ ), and magnesium bistrifluoromethanesulfonylimide (Mg(TFSI)) manufactured by Toyama Pharmaceutical Co., Ltd. ２ As the lithium salt, lithium trifluoromethanesulfonate (LiTFO) manufactured by Toyama Pharmaceutical Co., Ltd. was used. As the ether compound solvent, dimethoxyethane (DME) manufactured by Toyama Pharmaceutical Co., Ltd. was used.

[0039] Mg(TFSI) ２ and MgCl ２ The molar concentrations of ３ ,0.5mol / dm ３ This Mg(TFSI) ２ and MgCl ２ was dissolved in DME to give a concentration of 0.25 mol / dm ３ Mg(TFSI) ２ :0.5mol / dm ３ MgCl ２ After that, the molar concentration of LiTFO was adjusted to 1 mol / dm ３ This LiTFO was dissolved in the electrolyte to give a concentration of 0.25 mol / dm ３ Mg(TFSI) ２ :0.5mol / dm ３MgCl ２ : 1 mol / dm ３ A LiTFO / DME electrolyte was prepared.

[0040] The concentration of metal ions such as magnesium ions in the electrolyte is measured by ICP atomic emission spectrometry. The concentration of organic substances such as TFO ions is measured by NMR. The film thickness of the positive electrode active material layer and the negative electrode active material layer is obtained by observing a thinned negative electrode using an electron microscope (SEM), measuring the thickness of 10 or more negative electrode active material layers, and calculating the arithmetic average of the values.

[0041] The specific compositions of the electrolyte solutions according to Examples 1 to 3 are shown in Table 1. As shown in Table 1, in the electrolyte solution according to Example 1, the molar concentration of Mg was 0.75 mol / dm ３ , the molar concentrations of Li and TFO are 1 mol / dm ３ , the molar concentration of TFSI is 0.25 mol / dm ３ The concentration ratio of TFO to TFSI, TFO / TFSI, is 4.

[0042] As shown in Table 1, the electrolyte solution of Comparative Example 1 differs from that of Example 1 in that it does not contain LiTFO, i.e., it does not contain Li ions and TFO ions. ２ and MgCl ２ The molar concentrations are the same as in Example 1.

[0043]

[0044] The secondary battery 50 (coin cell) according to Example 1 used a magnesium (Mg) disk (diameter 16 mm) as the counter electrode 51. A surface-roughened nickel (Ni) foil (diameter 17 mm) was used as the working electrode 52.

[0045] The counter electrode 51 and the working electrode 52 are stacked with the separator 53 interposed between them, and are placed inside the anode cup 54 and the cathode cup 55, which are then crimped. In this way, the anode cup 54 and the cathode cup 55 are sealed to form an exterior body, thereby producing a coin cell.

[0046] The charge / discharge tests shown in Figures 3 and 4 were carried out under the following conditions: Discharge conditions: CC discharge 0.5 mA / 5 mAh cut Charge conditions: CC charge 0.5 mA / 2.5 V cut Temperature: 25 degrees Celsius

[0047] The Coulombic efficiency was calculated based on the formula: Coulombic efficiency (%) = (discharge capacity / charge capacity) × 100. In other words, the Coulombic efficiency is the ratio between the amount of Mg deposited on the Ni electrode (working electrode 52) during discharge and the amount of Mg stored on the Mg electrode (counter electrode 51) during charge. In each example and comparative example, a charge / discharge test was performed multiple cycles (e.g., three cycles), and the average value of the Coulombic efficiency calculated for each cycle is shown.

[0048] As shown in FIG. 4 , the secondary battery according to Comparative Example 1 sometimes experienced short circuits during charge / discharge testing, making it difficult to accurately measure the Coulombic efficiency. In contrast, as shown in FIG. 3 , the secondary battery 50 according to Example 1 experienced good charge / discharge behavior. That is, the capacity at the time when the voltage rose in the charge / discharge curve was close to the maximum capacity (5 mAh) of the discharge curve, indicating that dissolution and precipitation of Mg were performed well. As shown in Table 1, the Coulombic efficiency of the secondary battery 50 according to Example 1 was 99.6%, whereas measurement was not possible in Comparative Example 1 due to the occurrence of short circuits.

[0049] The above results show that the electrolyte solution of the secondary battery 50 according to Example 1 contains lithium ions and TFO ions (trifluoromethanesulfonate ions) in addition to magnesium ions and TFSI ions (bis(trifluoromethanesulfonyl)imide ions), and therefore the counter electrode 51 is activated more effectively than in the comparative example using an electrolyte solution that does not contain lithium ions or TFO ions, resulting in improved Coulombic efficiency.

[0050] (Example 2) Fig. 5 is a graph showing charge / discharge curves of a secondary battery according to Example 2. Fig. 6 is a graph showing charge / discharge curves of a secondary battery according to Comparative Example 2. Table 1 shows the molar concentrations and coulombic efficiencies of the electrolyte solutions according to Example 2 and Comparative Example 2.

[0051] Example 2 and Comparative Example 2 differ from Example 1 and Comparative Example 1 described above in that diethylene glycol dimethyl ether manufactured by Toyama Pharmaceutical Co., Ltd. is used as the solvent for the electrolyte solution instead of dimethoxyethane (DME). In Example 2, anthracene, a polycyclic aromatic hydrocarbon manufactured by Tokyo Chemical Industry Co., Ltd., is also used as an additive. In the following description, diethylene glycol dimethyl ether may be referred to as "G2" and anthracene may be referred to as "ANT."

[0052] The electrolyte solution according to Example 2 was Mg(TFSI) ２ , MgCl ２ and anthracene (ANT) molar concentrations of 0.4 mol / dm ３ ,0.4mol / dm ３ ,0.01mol / dm ３ This Mg(TFSI) ２ , MgCl ２ and ANT were dissolved in diethylene glycol dimethyl ether (G2) at 0.4 mol / dm ３ Mg(TFSI) ２ :0.4mol / dm ３ MgCl ２ :0.01mol / dm ３ The ANT / G2 electrolyte solution was obtained. After that, the molar concentration of LiTFO was adjusted to 1 mol / dm ３ This LiTFO was dissolved in the electrolyte to give a concentration of 0.4 mol / dm ３ Mg(TFSI) ２ :0.4mol / dm ３ MgCl ２ :0.01mol / dm ３ ANT: 1mol / dm ３ A LiTFO / G2 electrolyte was prepared.

[0053] The specific composition of the electrolyte solution according to Example 2 is shown in Table 1. As shown in Table 1, in the electrolyte solution according to Example 2, the molar concentration of Mg was 0.8 mol / dm ３ , the molar concentrations of Li and TFO are 1 mol / dm ３ , the molar concentration of TFSI is 0.4 mol / dm ３The concentration ratio of TFO to TFSI, TFO / TFSI, is 2.5.

[0054] As shown in Table 1, the electrolyte solution of Comparative Example 2 differs from that of Example 2 in that it does not contain LiTFO. ２ and MgCl ２ The molar concentrations are the same as in Example 2.

[0055] The configuration of the secondary battery 50 (coin cell) and the conditions for the charge / discharge test in Example 2 are the same as those in Example 1, and therefore repeated explanations will be omitted.

[0056] As shown in Fig. 5, the secondary battery 50 according to Example 2 was shown to be able to charge and discharge well, similar to Example 1 described above. In contrast, as shown in Fig. 6, the secondary battery according to Comparative Example 2 has a capacity when the voltage rises in the charge and discharge curve that is lower than the maximum capacity (5 mAh) in the discharge curve, compared to Example 2. As shown in Table 1, the coulombic efficiency of the secondary battery according to Comparative Example 2 is 89.3%, while the coulombic efficiency of the secondary battery 50 according to Example 2 is 96.8%.

[0057] The above results show that the secondary battery 50 according to Example 2 can improve the coulombic efficiency compared to Comparative Example 2, even when diethylene glycol dimethyl ether is used as the solvent for the electrolyte solution.

[0058] Example 3 Table 1 shows the molar concentrations and coulombic efficiencies of the electrolyte solutions according to Examples 3-1 to 3-7 and Comparative Example 3.

[0059] In Example 3, Mg(TFSI) ２ The charge-discharge curves and Coulombic efficiency are shown below when the molar concentration of LiTFO is varied while the molar concentration of Li is kept constant. In Example 3, dimethoxyethane (DME) was used as the solvent for the electrolyte solution, as in Example 1.

[0060] The electrolyte solution according to Example 3 was Mg(TFSI) ２ and MgCl ２ The molar concentrations of ３ ,0.5mol / dm ３This Mg(TFSI) ２ and MgCl ２ was dissolved in DME to give a concentration of 0.25 mol / dm ３ Mg(TFSI) ２ :0.5mol / dm ３ MgCl ２ After that, the molar concentration of LiTFO was adjusted to 0.1 mol / dm ３ 2mol / dm or more ３ Each component was weighed out so as to fall within the following range, and the LiTFO was dissolved in the above-mentioned electrolyte solution to prepare the electrolyte solution.

[0061] The specific composition of the electrolyte solution according to Example 3 is shown in Table 1. As shown in Table 1, in the electrolyte solutions according to Examples 3-1 to 3-7 and Comparative Example 3, the molar concentration of Mg was 0.75 mol / dm ３ and the molar concentration of TFSI is constant at 0.25 mol / dm ３ The molar concentrations of Li and TFO are constant at 0.05 mol / dm ３ More than 5mol / dm ３ The concentration ratio of TFO to TFSI, TFO / TFSI, is 0.1 or more and 10 or less.

[0062] As shown in Table 1, the secondary batteries 50 according to Examples 3-1 to 3-7 were prepared by using a lithium-containing battery with a molar concentration of 0.05 mol / dm ３ 3mol / dm or more ３ By setting the range as follows, the coulomb efficiency becomes 97% or more, and Comparative Example 3 (the molar concentration of Li and TFO is 5 mol / dm ３ ) provides better coulombic efficiency.

[0063] In other words, in the secondary batteries 50 according to Examples 3-1 to 3-7, by setting the concentration ratio TFO / TFSI of TFO to TFSI in the range of 0.1 to 6, a coulombic efficiency of 97% or higher can be obtained.

[0064] More preferably, the secondary batteries 50 according to Examples 3-2 to 3-7 have a molar concentration of Li and TFO of 0.1 mol / dm ３ 3mol / dm or more ３By setting the range as follows, a coulomb efficiency of 98% or more can be obtained.

[0065] In other words, in the secondary batteries 50 according to Examples 3-2 to 3-7, by setting the concentration ratio TFO / TFSI of TFO to TFSI in the range of 0.2 to 6, a coulombic efficiency of 98% or higher can be obtained.

[0066] More preferably, the secondary batteries 50 according to Examples 3-3 to 3-7 have a molar concentration of Li and TFO of 0.5 mol / dm ３ 3mol / dm or more ３ By setting the range as follows, a coulomb efficiency of 99% or more can be obtained.

[0067] In other words, in the secondary batteries 50 according to Examples 3-3 to 3-7, by setting the concentration ratio TFO / TFSI of TFO to TFSI in the range of 1 or more and 6 or less, a coulombic efficiency of 99% or more can be obtained.

[0068] The above results show that in Example 3, by varying the molar concentration of LiTFO, the activation state of the surface of the counter electrode 51 using magnesium metal changes, and that by setting the molar concentration within the above-mentioned range or the concentration ratio TFO / TFSI within the above-mentioned range, the Coulomb efficiency can be improved.

[0069] In the above-described Examples 1 to 3, Ni foil was used as the working electrode 52 to clarify the reaction of deposition and dissolution of magnesium in the combination of the counter electrode 51 using magnesium metal and the electrolyte solution shown in each Example. However, the present invention is not limited to this, and the positive electrode 10 described in the above-described embodiment can be used instead of the working electrode 52.

[0070] In the embodiment, the configuration of a secondary battery 1 is shown as an electrochemical device, but this is merely an example and is not limited thereto. The present disclosure can also be applied to other electrochemical devices, such as capacitors and fuel cells. Furthermore, the configuration of a coin-type or button-type battery is shown as the secondary battery 1, but is not limited thereto. The secondary battery 1 of the present disclosure may also be, for example, a cylindrical or laminate film type battery.

[0071] The above-described embodiment is intended to facilitate understanding of the present invention, and is not intended to limit the present invention. The present invention may be modified or improved without departing from the spirit and scope of the present invention, and equivalents thereof are also included in the present invention.

[0072] The present disclosure may also have the following configurations.

[0073] (1) An electrochemical device comprising: a negative electrode containing a magnesium-containing material; and an electrolyte solution containing lithium ions, magnesium ions, TFO ions (trifluoromethanesulfonate ions), and TFSI ions (bis(trifluoromethanesulfonyl)imide ions). (2) The concentration of the TFO ions in the electrolyte solution is 0.05 mol / dm ３ 3mol / dm or more ３ (3) The electrochemical device according to (1) or (2), wherein the concentration ratio of the TFO ions to the TFSI ions (TFO / TFSI) is 0.1 or more and 6 or less. (4) The concentration of the TFO ions in the electrolyte solution is 0.1 mol / dm or less. ３ 3mol / dm or more ３ (5) The electrochemical device according to (1), wherein the concentration ratio of the TFO ions to the TFSI ions (TFO / TFSI) is 0.2 or more and 6 or less. (6) The electrochemical device according to any one of (1) to (5), wherein the negative electrode has a negative electrode active material layer containing magnesium metal, lithium, aluminum, and zinc, and the content of the magnesium metal is 90 wt % or more, the content of the lithium is 10 wt % or less, the content of the aluminum is 10 wt % or less, and the content of the zinc is 2 wt % or less, based on the entire negative electrode active material layer. (7) The electrochemical device according to any one of (1) to (6), wherein the negative electrode has a negative electrode active material layer and a negative electrode current collector supporting the negative electrode active material layer, and the film thickness of the negative electrode active material layer is 5 μm or more, and the negative electrode active material layer is provided on one or both sides of the negative electrode current collector. (8) The concentration of the magnesium ions in the electrolyte is 0.5 mol / dm ３The electrochemical device according to (1) above.

[0074] 1, 50 Secondary battery 10 Positive electrode 20 Negative electrode 30, 53 Separator 51 Counter electrode 52 Working electrode 54 Anode cup 55 Cathode cup

Claims

1. An electrochemical device having a negative electrode including a magnesium-containing material and an electrolyte including lithium ions, magnesium ions, TFO ions (trifluoromethanesulfonate ions), and TFSI ions (bis(trifluoromethanesulfonyl)imide ions).

2. The concentration of the TFO ions in the electrolyte is 0.05 mol / dm ３ 3mol / dm or more ３ The electrochemical device according to claim 1 , wherein:

3. The electrochemical device according to claim 1 or 2, wherein the concentration ratio of the TFO ions to the TFSI ions (TFO / TFSI) is 0.1 or more and 6 or less.

4. The concentration of the TFO ions in the electrolyte is 0.1 mol / dm ３ 3mol / dm or more ３ The electrochemical device according to claim 1 , wherein:

5. The electrochemical device according to claim 1 or 4, wherein the concentration ratio of the TFO ions to the TFSI ions (TFO / TFSI) is 0.2 or more and 6 or less.

6. The electrochemical device according to any one of claims 1 to 5, wherein the negative electrode has a negative electrode active material layer containing magnesium metal, lithium, aluminum, and zinc, and the magnesium metal content is 90 wt% or more, the lithium content is 10 wt% or less, the aluminum content is 10 wt% or less, and the zinc content is 2 wt% or less, based on the entire negative electrode active material layer.

7. The electrochemical device according to any one of claims 1 to 6, wherein the negative electrode comprises a negative electrode active material layer and a negative electrode current collector supporting the negative electrode active material layer, the negative electrode active material layer having a thickness of 5 μm or more, and the negative electrode active material layer is provided on one or both sides of the negative electrode current collector.

8. The concentration of the magnesium ions in the electrolyte is 0.5 mol / dm ３ The electrochemical device according to claim 1 , wherein

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