Electrolyte used in magnesium secondary batteries, method for preparing the same, and magnesium secondary battery

Abstract

The present application provides an electrolyte solution for use in a magnesium secondary battery, the electrolyte solution containing an electrolyte salt and a non-aqueous solvent, a method for preparing the electrolyte solution, and a magnesium secondary battery. The electrolyte contains an electrolyte salt and a non-aqueous solvent. The electrolyte salt contains [Mg x M 2x-1 P y ][Mg(OR F )3Q z wherein x is an integer between 1 and 6, y is an integer between 1 and 6, z is an integer between 0 and 6, M is a -1-valent ion, R F each independently represents a partially or fully fluorinated C1 to C6 aliphatic hydrocarbon group, or a partially or fully fluorinated C6 to C12 aromatic hydrocarbon group, and P and Q represent a complexing agent. The electrolyte provided by the present application has excellent electrochemical performance and also has high interfacial stability between the electrolyte and the negative electrode.

Description

[Technical Field]

[0001] This application claims priority to Chinese Patent Application No. 202210134125.8, filed on 14 February 2022, titled "Electrolyte for use in a magnesium secondary battery, method for preparing the same, and magnesium secondary battery," all contents of said application are incorporated herein by reference.

[0002] This application relates to the field of electrochemistry, and more specifically to an electrolyte used in a magnesium secondary battery, a method for preparing the same, and a magnesium secondary battery. [Background technology]

[0003] The development of rechargeable secondary batteries is key to solving the problem of renewable energy storage. In recent years, metallic magnesium has become popular because it is abundant, inexpensive, environmentally friendly, has stable physicochemical properties, and has a high theoretical volumetric specific capacity (3833 mAh / cm³). 3 Due to its advantages such as those mentioned above, magnesium secondary batteries, which use metallic magnesium as the negative electrode, are currently one of the most promising new energy storage systems. However, the development of magnesium secondary batteries is currently very slow, and the electrolyte is one of the important factors that constrains its development. [Overview of the project] [Problems that the invention aims to solve]

[0004] In light of this, there is a need to provide an electrolyte solution applicable to magnesium secondary batteries.

[0005] This invention provides an electrolyte for use in a magnesium secondary battery, a method for preparing the same, and a magnesium secondary battery, wherein the electrolyte has excellent electrochemical properties and high interfacial stability between the electrolyte and the negative electrode.

[0006] A first aspect of the present application provides an electrolyte for use in a magnesium secondary battery, comprising an electrolyte salt and a non-aqueous solvent, wherein the electrolyte salt is [Mg x M2x-1 P y [Mg(OR F )3Q z , where x represents an integer between 1 and 6, y represents an integer between 1 and 6, z represents an integer between 0 and 6, M represents a -1 valence ion, and R F each independently represents a C1 - C6 aliphatic hydrocarbon group that is partially fluorinated or fully fluorinated, or a C6 - C12 aromatic hydrocarbon group that is partially fluorinated or fully fluorinated, and P and Q represent complexing agents.

[0007] The inventor of the present application unexpectedly discovered that in the research of the electrolyte of a magnesium secondary battery, when the electrolyte contains [Mg x M 2x-1 P y [Mg(OR F )3Q z , the electrolyte can have excellent electrochemical performance, and at the same time, the interfacial stability between the electrolyte and the negative electrode is also high. Furthermore, the magnesium secondary battery using it can have excellent electrochemical performance and a long cycle life.

[0008] In any embodiment of the present application, the cation of the electrolyte salt is [Mg x M 2x-1 P y + , and the anion is [Mg(OR F )3Q z - .

[0009] In any embodiment of the present application, P and Q are the same.

[0010] In any embodiment of the present application, M represents one or more of F - , Cl - , Br - , I - , HMDS - , CF3 - , (CF3SO2)2N - . Preferably, M represents F - , Cl - , Br - , I​​- It represents one or more types of these.

[0011] In any embodiment of the present application, R F Each of these independently represents a C1-C6 alkyl group, a phenyl group, a C6-C12 alkylphenyl group, or a C6-C12 phenylalkyl group, which are partially or fully fluorinated. Preferably, R F Each of these independently represents methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, phenyl, methylphenyl, ethylphenyl, n-propylphenyl, t-butylphenyl, phenylmethyl, and phenylethyl, which are partially or fully fluorinated.

[0012] In any embodiment of the present application, the non-aqueous solvent, complexing agent P, and complexing agent Q each independently represent one or more types of ionic liquids and a first organic solvent.

[0013] In any embodiment of the present application, the ionic liquid includes one or more types of imidazole-based ionic liquids, piperidine-based ionic liquids, and pyrrole-based ionic liquids.

[0014] In any embodiment of the present application, the imidazole-based ionic liquid comprises one or more of the following: 1-ethyl-3-methylimidazolium tetrafluoroborate salt, 1-ethyl-3-methylimidazolium hexafluorophosphate salt, and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide salt.

[0015] In any embodiment of the present application, the pyrrole-based ionic liquid comprises an N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide salt.

[0016] In any embodiment of the present application, the piperidine-based ionic liquid comprises an N-butyl-N-methylpiperidinium bis(trifluoromethylsulfonyl)imide salt.

[0017] In any embodiment of the present application, the first organic solvent includes one or more of the following: ether solvents, imidazole solvents, pyridine solvents, sulfone solvents, ester solvents, aromatic hydrocarbon solvents, amide solvents, and nitrile solvents.

[0018] In any embodiment of the present application, the ether solvent includes one or more of the following: dioxolane, tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and polyethylene glycol dimethyl ether.

[0019] In any embodiment of the present application, the pyridine solvent includes one or more of the following: pyridine, 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, 2,6-dichloropyridine, and 2-aminopyridine.

[0020] In any embodiment of the present application, the ester solvent includes one or more of ethylene carbonate and ethyl acetate.

[0021] In any embodiment of the present application, the non-aqueous solvent, complexing agent P, and complexing agent Q are the same.

[0022] In any embodiment of the present application, [Mg in the electrolyte] x M 2x-1 P y ][Mg(OR F )3Q z The concentration of [Mg] is 0.1 mol / L to 1.2 mol / L. Preferably, [Mg] x M 2x-1 P y ][Mg(OR F )3Q z The concentration of [ ] is 0.1 mol / L to 0.8 mol / L.

[0023] A second aspect of the present application provides a method for preparing an electrolyte used in the preparation of the electrolyte in the first aspect of the present application, and Mg(OR FStep S100 provides Mg(OR F )2. After mixing anhydrous MgM2 and a non-aqueous solvent, 25 o C~100 o The process includes step S200, in which an electrolyte is obtained by reacting with C.

[0024] In any embodiment of the present application, the reaction time for S200 is 3h to 48h.

[0025] In any embodiment of the present application, Mg(OR) relative to anhydrous MgM2 F The molar ratio of )2 is 1:(0.5~3.0), preferably 1:(0.8~2.0).

[0026] In any embodiment of the present application, Mg(OR F )2 is obtained by the following preparation method: HOR F After mixing with MgR2, 0 o C~200 o After reacting with C and removing the second organic solvent by drying, Mg(OR F )2 was obtained. Here, MgR2 represents a magnesium alkoxide or magnesium alkyl salt.

[0027] In any embodiment of the present application, MgR2 is selected from magnesium methoxide, magnesium ethoxide, magnesium propoxide, dibutylmagnesium, or ethyl magnesium chloride.

[0028] In any embodiment of the present application, the second organic solvent includes one or more of the following: ether solvents, imidazole solvents, pyridine solvents, sulfone solvents, ester solvents, aromatic hydrocarbon solvents, amide solvents, and nitrile solvents.

[0029] A third aspect of the present application provides a magnesium secondary battery comprising the electrolyte of the first aspect of the present application or an electrolyte prepared using the method of the second aspect of the present application. [Effects of the Invention]

[0030] This invention has the following beneficial effects. The electrolyte of this invention has excellent electrochemical properties, and at the same time, high interfacial stability between the electrolyte and the negative electrode. The electrolyte preparation method of this invention is simple in its process and can meet the needs for the commercialization of magnesium secondary batteries. The magnesium secondary battery using the electrolyte of this invention has excellent electrochemical performance and a long cycle life. [Brief explanation of the drawing]

[0031] To more clearly explain the technical solutions in the embodiments of the present application, the necessary drawings used in the embodiments of the present application will be briefly described below. However, obviously, the drawings described below represent only a few embodiments of the present application, and other drawings can be obtained based on these drawings without requiring any creative work from those skilled in the art. [Figure 1] The mass spectrometry results of the electrolyte prepared according to Comparative Example 1 are shown. Figure 1(a) shows the analysis results of the anionic portion of the electrolyte, and Figure 1(b) shows the analysis results of the cation portion of the electrolyte. [Figure 2] The mass spectrometry results of the anionic portion in the electrolyte prepared according to Example 1 are shown. [Figure 3] The diagram shows a comparison of the Raman spectral measurement results of the electrolytes and THF solvents prepared in Example 1 and Comparative Example 2. I represents the electrolyte prepared in Example 1, II represents the electrolyte prepared in Comparative Example 2, and III represents the THF solvent. [Figure 4] The linear scanning LSV curve of the Mg / / Pt half-cell assembled with the electrolyte prepared in Example 1 is shown. [Figure 5] The cyclic voltammetry CV curve of the Mg / / Pt half-cell assembled with the electrolyte prepared in Example 1 is shown. [Figure 6] The circulating sedimentation dissolution potential curve of a Mg / / Mg symmetric half-cell assembled with the electrolyte prepared in Example 1 is shown. [Figure 7]The electrochemical impedance spectroscopy obtained by fitting the equivalent circuit of the Mg / / Mg symmetric half-cell assembled with the electrolyte prepared in Example 1 to a Nyquist diagram is shown. [Figure 8] The charge-discharge curve diagram for the first cycle of a magnesium-ion battery assembled using the electrolyte prepared in Example 1 is shown. [Figure 9] The circulation curve diagram of a magnesium-ion battery assembled using the electrolyte prepared in Example 1 is shown. [Modes for carrying out the invention]

[0032] To clarify the purpose of the present invention, the technical solution, and the beneficial technical effects, the present application will be described in more detail below with reference to the examples. It should be understood that the examples described herein are for interpretation purposes only and are not intended to limit the present application.

[0033] For the sake of simplification, only a few numerical ranges are explicitly disclosed in this text. However, any lower limit can be combined with any upper limit to form an unspecified range, and any lower limit can be combined with other lower limits to form an unspecified range. Similarly, any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, although not specified, each point or single number between the endpoints of a range is included within that range. Thus, each point or single number, as its own lower or upper limit, can be combined with any other point or single number, or with any other lower or upper limit, to form an unspecified range.

[0034] In the text, unless otherwise specified, "above" and "below" include the number of items, and "several types (items)" in "one or more types" and "one or more" means two or more types (items).

[0035] In this application, the term "aliphatic hydrocarbon group" refers to a chain-like group having the basic properties of an aliphatic compound, and includes alkyl groups, alkenyl groups, and alkyne groups. The above groups may have a linear or branched structure. In each example, the C1-C6 aliphatic hydrocarbon group, i.e., the aliphatic hydrocarbon group, may contain 1 to 6 carbon atoms.

[0036] In this application, the term "aromatic hydrocarbon group" means a carbocyclic system having aromatic properties, and the carbocyclic structure may be monocyclic, polycyclic, or bicyclic, and the carbocyclic structure may or may not contain substituents, where the substituent may be one or more of alkyl groups, alkenyl groups, or alkyne groups, and the number of substituents may be one or more. In each embodiment, the C6-C12 aromatic hydrocarbon group, i.e., the aromatic hydrocarbon group, may contain 6 to 12 carbon atoms.

[0037] In this application, the term "partially fluorinated or fully fluorinated C1-C6 aliphatic hydrocarbon group" means that at least one hydrogen atom in the C1-C6 aliphatic hydrocarbon group is substituted with a fluorine atom.

[0038] In this application, the term "partially fluorinated or fully fluorinated C6-C12 aromatic hydrocarbon group" means that at least one hydrogen atom in the C6-C12 aromatic hydrocarbon group is substituted with a fluorine atom, where at least one hydrogen atom on the carbocyclic structure may be substituted with a fluorine atom, at least one hydrogen atom of a substituent connected to the carbocyclic structure (for example, one or more of alkyl groups, alkenyl groups, or alkyne groups) may be substituted with a fluorine atom, and at least one hydrogen atom in the carbocyclic structure and the substituents connected thereto may be substituted with a fluorine atom. For example, "partially fluorinated or fully fluorinated methylphenyl" means that the fluorine atom can be located in at least one of the methyl group and the benzene ring structure.

[0039] Throughout this specification, substituents of compounds are disclosed by group or range. Such descriptions are expressly intended to include each individual subcombination of members of these groups and ranges. For example, the term “C1-C6 aliphatic hydrocarbon group” is expressly intended to disclose the C1, C2, C3, C4, C5, C6, C1-C6, C1-C5, C1-C4, C1-C3, C1-C2, C2-C6, C2-C5, C2-C4, C2-C3, C3-C6, C3-C5, C3-C4, C4-C6, C4-C5 and C5-C6 aliphatic hydrocarbon groups individually.

[0040] A magnesium secondary battery mainly consists of a positive electrode, a negative electrode, and an electrolyte, where the positive electrode contains a positive electrode material capable of intercalating and deintercalating magnesium ions, and the negative electrode is usually metallic magnesium or a magnesium alloy. The operating principle of a magnesium secondary battery is usually as follows: When the battery is charged, magnesium ions deintercalate from the positive electrode material and settle on the negative electrode surface in the form of magnesium elements via the electrolyte. When the battery is discharged, magnesium ions dissolve from the negative electrode, move to the positive electrode surface via the electrolyte, and then intercalate into the positive electrode material.

[0041] Because magnesium ions have a high charge density and a low reduction potential (-2.37V vs. standard hydrogen electrode), most organic solvents and electrolytes can react with metallic magnesium, etc., and form a passivation layer on the negative electrode surface that does not effectively conduct magnesium ions, affecting the reversible precipitation and dissolution of metallic magnesium and significantly hindering the operation of magnesium secondary batteries. Furthermore, metallic magnesium, etc., is also susceptible to the effects of impurities (e.g., trace amounts of water, oxygen, carbon dioxide, etc.), and during long charge-discharge processes, the interface between the negative electrode and electrolyte tends to become unstable, hindering the conduction of magnesium ions. In addition, large overpotentials during battery charge and discharge lead to uneven precipitation and dissolution of metallic magnesium, which can ultimately lead to problems such as short circuits within the battery.

[0042] Currently, the development of electrolytes for magnesium secondary batteries is still in its early stages. Conventional electrolytes mainly include Grignard reagent systems, hexamethyldisilazane (HMDS) systems, trifluoromethanesulfonyliimide (TFSI) systems, all-inorganic magnesium salt systems, and boron systems. However, these electrolytes typically have complex preparation processes, low solubility of electrolyte salts, and unstable electrochemical properties, hindering the development of magnesium secondary batteries.

[0043] In light of this, in order to meet the commercialization needs of magnesium secondary batteries, there is a need to provide an electrolyte that is easy to prepare, has excellent electrochemical properties, and has high interfacial stability with the negative electrode.

[0044] In a first embodiment of the present invention, an electrolyte solution for use in a magnesium secondary battery is provided, comprising an electrolyte salt and a non-aqueous solvent. The electrolyte salt is [Mg x M 2x-1 P y ][Mg(OR F )3Q z ] includes, where x represents an integer between 1 and 6, y represents an integer between 1 and 6, z represents an integer between 0 and 6, M represents a -1 valent ion, and R F Each of the following independently represents a C1-C6 aliphatic hydrocarbon group that is partially or fully fluorinated, and an aromatic hydrocarbon group that is partially or fully fluorinated, while P and Q represent complexing agents.

[0045] In the electrolyte of the present invention, the cation of the electrolyte salt is [Mg x M 2x-1 P y ] + It contains anions [Mg(OR F )3Q z ] - It includes. In some examples, the cation of the electrolyte salt is [Mg x M 2x-1 P y ] + It contains anions [Mg(OR F )3Q z ] - Includes.

[0046] In the research on the electrolyte of magnesium secondary batteries, the inventor of the present application found that a single anhydrous magnesium salt MgM2 (for example, MgCl2, etc.) is difficult to dissociate in a non-aqueous solvent to form cations, and it is also difficult to form a solid electrolyte interphase (i.e., SEI) that can conduct magnesium ions on the surface of the negative electrode. Therefore, it is difficult for an electrolyte using MgM2 to have excellent electrochemical performance. A single magnesium salt Mg(OR F )2 can dissociate in a non-aqueous solvent to form cations and anions, but the electrolyte prepared thereby has a low ionic conductivity and it is also difficult to have excellent electrochemical characteristics.

[0047] In the research on the electrolyte of magnesium secondary batteries, the inventor of the present application found that when [Mg x M 2x-1 P y [Mg(OR F )3Q z is included in the electrolyte, the electrolyte can have excellent electrochemical performance, and at the same time, the interfacial stability between the electrolyte and the negative electrode is high. Furthermore, it was unexpectedly found that a magnesium secondary battery using it can have excellent electrochemical performance and a long cycle life. Although the mechanism is not clear, the reasons speculated by the inventor of the present application include the following several. 1. [Mg x M 2x-1 P y [Mg(OR F )3Q z has a high solubility in the electrolyte and dissociates under the action of the non-aqueous solvent of the electrolyte to form cations [Mg x M 2x-1 P y + and anions [Mg(OR F )3Q z - that have stable and high magnesium ion transport performance, thereby ensuring that the electrolyte of the present application has a high ionic conductivity and further ensuring the efficient transmission of magnesium ions. 2. [Mg x M 2x-1 P​​y [Mg(OR F )3Q z [Mg(OR)3Q] helps to form a SEI with low impedance on the surface of the negative electrode, which can conduct magnesium ions and has stable performance. On the one hand, it ensures the efficient transmission of magnesium ions, improves the ability of the electrolyte to reversibly precipitate and dissolve metallic magnesium, and further ensures that the electrolyte has excellent electrochemical properties. On the other hand, it stabilizes the interface between the negative electrode and the electrolyte, reduces the direct contact between metallic magnesium and impurities (such as trace amounts of water, oxygen, carbon dioxide, etc.), and further reduces the probability of problems such as large charge-discharge overpotential of the battery, non-uniform precipitation and dissolution of metallic magnesium, and thus short circuit inside the battery. 3.[Mg x M 2x-1 P y [Mg(OR F )3Q z [Mg(OR)3Q] has good compatibility with the positive electrode material and helps to increase the electrochemical window of the electrolyte.

[0048] x represents an integer between 1 and 6, that is, x can represent 1, 2, 3, 4, 5 or 6. Preferably, x represents 1, 2, 3 or 4. Further, x represents 1, 2 or 3.

[0049] y represents an integer between 1 and 6, that is, y can represent 1, 2, 3, 4, 5 or 6. Preferably, y represents 1, 2, 3 or 4. Further, y represents 1, 2 or 3.

[0050] z represents an integer between 0 and 6. In some embodiments, z can represent 0. In some embodiments, z represents an integer between 1 and 6, that is, z can represent 1, 2, 3, 4, 5 or 6, preferably, z represents 1, 2, 3 or 4, and further, z represents 1, 2 or 3.

[0051] M represents a monovalent ion. In some embodiments, M is F - , Cl - , Br - , I - , HMDS -(Hexamethyldisilazaneion, [(CH3)3Si]2N - ), CF3 SO3 - (OTf - ), (CF3SO2)2N - (TFSI - ) can represent one or more types. Preferably, M is F - Cl - , Br - , I - It represents one or more types of these. Furthermore, M is Cl - It represents.

[0052] R F represents a fluorine-containing organic group. Here, a partially or fully fluorinated C1-C6 aliphatic hydrocarbon group includes a partially or fully fluorinated C1-C6 alkyl group, a C1-C6 alkenyl group, or a C1-C6 alkyne group, preferably including a partially or fully fluorinated C1-C6 alkyl group. A partially or fully fluorinated C6-C12 aromatic hydrocarbon group includes a phenyl group, a C6-C12 alkylphenyl group, a C6-C12 alkenylphenyl group, a C6-C12 alkynephenyl group, a C6-C12 phenylalkyl group, a C6-C12 phenylalkenyl group, or a C6-C12 phenylalkyne group, preferably including a partially or fully fluorinated C6-C12 aromatic hydrocarbon group, a C6-C12 alkylphenyl group, or a C6-C12 phenylalkyl group.

[0053] In some examples, R F Each of these independently represents a C1-C6 alkyl group, a phenyl group, a C6-C12 alkylphenyl group, or a C6-C12 phenylalkyl group, which are partially or fully fluorinated. Preferably, R FEach of these independently represents partially or fully fluorinated methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, phenyl, methylphenyl (including ortho, meta, and para), ethylphenyl (including ortho, meta, and para), n-propylphenyl (including ortho, meta, and para), t-butylphenyl (including ortho, meta, and para), phenylmethyl, and phenylethyl. Furthermore, R F These terms independently represent methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, phenyl, methylphenyl (including ortho, meta, and para), ethylphenyl (including ortho, meta, and para), n-propylphenyl (including ortho, meta, and para), t-butylphenyl (including ortho, meta, and para), phenylmethyl, and phenylethyl.

[0054] In some examples, [Mg x M 2x-1 P y ][Mg(OR F )3Q z The three R's in ] F They are the same.

[0055] P and Q represent complexing agents. Here, the complexing agent P and the -1 valent ion M coordinate simultaneously to form a +1 valent cation group [Mg x M 2x-1 P y ] + It forms a complex with complexing agent Q and fluorine-containing group -OR F It coordinates simultaneously to form a -1 valent anionic group [Mg(OR F )3Q z ] - It forms.

[0056] In some examples, complexing agent P and complexing agent Q may be the same. In this case, [Mg x M 2x-1 P y ][Mg(OR F )3Q z ] dissociates into a cation [Mg x M 2x-1 P y ] +and anions [Mg(OR F )3Q z ] - It makes it easier to form the cation [Mg x M 2x-1 P y ] + and anions [Mg(OR F )3Q z ] - It is more stable.

[0057] In some examples, the non-aqueous solvent, complexing agent P, and complexing agent Q may be the same. Preferably, complexing agents P and Q can be derived from a non-aqueous solvent.

[0058] In some examples, the non-aqueous solvent, complexing agent P, and complexing agent Q each independently represent one or more types of ionic liquids and a first organic solvent.

[0059] The ionic liquid includes, but is not limited to, one or more of the imidazole-based ionic liquid, piperidine-based ionic liquid, and pyrrole-based ionic liquid. For example, the imidazole-based ionic liquid may include one or more of the following: 1-ethyl-3-methylimidazolium tetrafluoroborate salt, 1-ethyl-3-methylimidazolium hexafluorophosphate salt, and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide salt. For example, the pyrrole-based ionic liquid may include N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide salt. For example, the piperidine-based ionic liquid may include N-butyl-N-methylpiperidinium bis(trifluoromethylsulfonyl)imide salt.

[0060] For example, the first organic solvent includes, but is not limited to, one or more of the following: ether solvents, imidazole solvents, pyridine solvents, sulfone solvents, ester solvents, aromatic hydrocarbon solvents, amide solvents, and nitrile solvents. For example, ether solvents may include one or more of the following: dioxolane, tetrahydrofuran (THF), ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and polyethylene glycol dimethyl ether. For example, pyridine solvents may include one or more of the following: pyridine, 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, 2,6-dichloropyridine, and 2-aminopyridine. For example, ester solvents may include one or more of the following: ethylene carbonate and ethyl acetate.

[0061] In some examples, preferably, complexing agent P and complexing agent Q each independently represent an ether-based solvent. Furthermore, complexing agent P and complexing agent Q each independently represent one or more of the following: dioxolane, tetrahydrofuran (THF), ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and polyethylene glycol dimethyl ether.

[0062] In some examples, [Mg in the electrolyte] x M 2x-1 P y ][Mg(OR F )3Q z The concentration of [Mg] is 0.1 mol / L to 1.2 mol / L. For example, [Mg x M 2x-1 P y ][Mg(OR F )3Q zThe concentration of [Mg] is within the range of 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, 1.1 mol / L, 1.2 mol / L, or any of the above values. Preferably, [Mg] x M 2x-1 P y ][Mg(OR F )3Q z The concentration of [ ] is 0.1 mol / L to 0.8 mol / L.

[0063] Of course, the electrolyte of this application is [Mg x M 2x-1 P y ][Mg(OR F )3Q z This does not exclude other electrolyte salts other than those specified above. Other electrolyte salts may be, for example, Grignard reagent systems, hexamethyldisilazane (HMDS) systems, trifluoromethanesulfonyliimide (TFSI) systems, all-inorganic magnesium salt systems, boron systems, and other electrolyte salts known in the art that are applied to the electrolytes of magnesium secondary batteries.

[0064] A second aspect of the embodiments of the present application provides a method for preparing an electrolyte, Mg(OR F Step S100 provides Mg(OR F )2. After mixing anhydrous MgM2 and a non-aqueous solvent, 25 o C~100 o The process includes step S200, in which an electrolyte is obtained by reacting with C.

[0065] The preparation method of the second embodiment in the present invention can prepare the electrolyte of any embodiment of the first embodiment in the present invention. The parameters related to the electrolyte prepared by the above preparation method can refer to those of the electrolyte provided in each embodiment of the first embodiment in the present invention.

[0066] The electrolyte preparation method of this invention is simple in its process and can meet the needs for the commercialization of magnesium secondary batteries.

[0067] In some embodiments, the reaction time for S200 may be 3 to 48 hours, but the present invention is not limited thereto.

[0068] In some examples, Mg(OR) relative to anhydrous MgM2 F The molar ratio of )2 may be 1:(0.5~3.0). For example, Mg(OR) to anhydrous MgM2 F The molar ratio of )2 may be within the range of 1:0.5, 1:0.8, 1:1.0, 1:1.2, 1:1.4, 1:1.6, 1:1.8, 1:2.0, 1:2.2, 1:2.4, 1:2.6, 1:2.8, 1:3.0 or any of the above values. Preferably, Mg(OR) to anhydrous MgM2. F The molar ratio of )2 is 1:(0.8~2.0).

[0069] In some examples, Mg(OR F )2 is obtained by the following preparation method: HOR F After mixing with MgR2, 0 o C~200 o After reacting with C and removing the second organic solvent by drying, Mg(OR F )2 was obtained. Here, MgR2 represents a magnesium alkoxide or magnesium alkyl salt.

[0070] Preferably, the reaction time is 6 to 72 hours, but this invention is not limited thereto.

[0071] Preferably, MgR2 is selected from magnesium methoxide, magnesium ethoxide, magnesium propoxide, dibutylmagnesium, or ethyl magnesium chloride.

[0072] Preferably, the second organic solvent contains one or more of an ether solvent, an imidazole solvent, a pyridine solvent, a sulfone solvent, an ester solvent, an aromatic hydrocarbon solvent, an amide solvent, and a nitrile solvent. As an example, the ether solvent can contain one or more of dioxolane, tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and polyethylene glycol dimethyl ether. As an example, the pyridine solvent can contain one or more of pyridine, 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, 2,6-dichloropyridine, and 2-aminopyridine. As an example, the ester solvent can contain one or more of ethylene carbonate and ethyl acetate.

[0073] In a third aspect of the embodiments of the present application, a magnesium secondary battery including the electrolytic solution of the first aspect in the embodiments of the present application or the electrolytic solution prepared by using the method of the second aspect in the embodiments of the present application is provided, whereby the magnesium secondary battery of the present application can have excellent electrochemical performance and a long cycle life.

[0074] In some embodiments, the magnesium secondary battery further includes a positive electrode, a negative electrode, and a separator.

[0075] The positive electrode includes a positive electrode material capable of intercalating and deintercalating magnesium ions. Preferably, the positive electrode material includes one or more of transition metal sulfides, transition metal oxides, transition metal borides, and polyanionic phosphates, but is not limited thereto. As an example, the transition metal sulfides can include one or more of TiS2, MoS2, WS2, VS2, HfS2, ZrS2, NbS3, VS4, Mg a Mo3S4(0 < a < 2), and Mo6S8. As an example, the transition metal oxides are V2O5, V6O 13can contain one or several of MnO2, Mn2O3, MoO3, WO3. For example, the transition metal boride can contain one or several of TiB2, MoB2, ZrB2.

[0076] The negative electrode contains one or several of metallic magnesium and magnesium alloys, but is not limited thereto. For example, the magnesium alloy can contain one or several of magnesium-aluminum alloy, magnesium-silver alloy, and magnesium-copper alloy.

[0077] The separator is installed between the positive electrode and the negative electrode and mainly plays a role in preventing the short circuit between the positive electrode and the negative electrode. The present application is not particularly limited to the type of separator, and any known porous structure film having excellent chemical stability and mechanical stability can be used. For example, the separator includes, but is not limited to, a PE film, a PP film, a non-woven fabric, a glass fiber film (for example, a GF / B film), or a multilayer composite film thereof.

[0078] In some embodiments, the magnesium secondary battery may be a magnesium-sulfur secondary battery. Preferably, the positive electrode material contains one or several of TiS2, MoS2, WS2, VS2, HfS2, ZrS2, NbS3, VS4, Mg a Mo3S4(0 < a < 2), Mo6S8, etc., but is not limited thereto.

[0079] Hereinafter, the present application will be further described in accordance with the examples. It should be understood that these examples are for merely illustrative purposes since various modifications and changes within the scope of the disclosure of the present application will be apparent to those skilled in the art. Unless otherwise specified, all parts, percentages, and ratios reported in the following examples are all on a mass basis. All reagents used in the examples are commercially available or obtained by synthesis according to conventional methods, and can be directly used without treatment. All equipment used in the examples can be obtained commercially.

[0080] (Comparative Example 1) twenty five o Under a C environment, in an argon gas-atmosphered glove box with oxygen and water content of less than 1 ppm, perfluoro-t-butanol HOC(CF3)3 and magnesium methoxide Mg(OCH3)2 were reacted with a molar ratio of 3:1 in an appropriate amount of tetrahydrofuran (THF) for 24 hours with stirring. After removing the THF by drying, perfluoro-t-butanol magnesium salt Mg(pftb)2 was obtained. The prepared perfluoro-t-butanol magnesium salt Mg(pftb)2 was dissolved in an appropriate amount of THF to obtain an electrolyte. Here, the concentration of Mg(pftb)2 is 0.3 mol / L.

[0081] (Comparative Example 2) twenty five o Under a C environment, an electrolyte was obtained by dissolving anhydrous magnesium chloride (MgCl2) in an appropriate amount of THF in an argon gas-atmosphere glove box with an oxygen and water content of less than 1 ppm. Here, the concentration of MgCl2 was 0.3 mol / L.

[0082] (Example 1) After obtaining perfluoro-t-butanol magnesium salt Mg(pftb)2 by the same method as in Comparative Example 1, 25 o Under C conditions, the prepared perfluoro-t-butanol magnesium salt Mg(pftb)2 and anhydrous magnesium chloride MgCl2 were reacted with an appropriate amount of THF in a molar ratio of 3:1, stirring for 24 hours until clear, to obtain an electrolyte containing [Mg2Cl3·6THF][Mg(pftb)3]. Here, the concentration of [Mg2Cl3·6THF][Mg(pftb)3] is 0.3 mol / L.

[0083] Figure 1 shows the mass spectrometry results of the electrolyte prepared according to Comparative Example 1. Figure 1(a) shows the analysis results of the anionic portion of the electrolyte, and Figure 1(b) shows the analysis results of the cation portion of the electrolyte. The mass spectrometry results in Figure 1 reveal that perfluoro-t-butanol magnesium salt Mg(pftb)2 can dissociate in THF to form anions and cations.

[0084] Figure 2 shows the mass spectrometry results of the anionic portion in the electrolyte prepared according to Example 1. As can be seen from the comparison between Figure 2 and Figure 1, [Mg2Cl3·6THF][Mg(pftb)3] dissociates to form the anion [Mg(pftb)3]. - It formed.

[0085] Figure 3 shows a comparison of the Raman spectral measurement results of the electrolytes and THF solvents prepared in Example 1 and Comparative Example 2. I represents the electrolyte prepared in Example 1, II represents the electrolyte prepared in Comparative Example 2, and III represents the THF solvent. The Raman spectral measurement results in Figure 3 show that [Mg2Cl3·6THF] and [Mg(pftb)3] dissociate into the cation [Mg2Cl3·6THF]. + This reveals that it was formed.

[0086] In accordance with the measurement results in Figures 2 and 3, the electrolyte prepared in Example 1 simultaneously contains the anion [Mg(pftb)3] - and the cation [Mg2Cl3·6THF] + The inventors of this application speculate that the reaction mechanism between perfluoro-t-butanol magnesium salt Mg(pftb)2, anhydrous magnesium chloride MgCl2 and THF is as follows.

[0087] [ka]

[0088] To detect the oxidation stability and the ability to precipitate and dissolve metallic magnesium of the electrolyte of the present invention, the inventors measured the linear scanning LSV curve and cyclic voltammetry CV curve of the electrolyte prepared in Example 1 in a Mg / / Pt half-cell (with a GF / B film as a separator), and the measurement results are shown in Figures 4 and 5, respectively. The measurement results in Figures 4 and 5 show that the oxidation stability window of the electrolyte prepared in Example 1 is 3.0V (vs. Mg 2+ We demonstrate that it is possible to achieve a value greater than that of / Mg and to realize efficient reversible precipitation and dissolution of metallic magnesium.

[0089] To detect the interfacial stability between metallic magnesium and the electrolyte, the inventors of this application further measured the electrochemical impedance spectroscopy obtained by fitting the circulating sedimentation dissolution potential curve and equivalent circuit of the electrolyte prepared in Example 1 to a Nyquist diagram in a Mg / / Mg symmetric half-cell (with a GF / B film as a separator), and the measurement results are shown in Figures 6 and 7, respectively.

[0090] As can be seen from Figure 6, the Mg / / Mg symmetric half-cell exhibits a small polarization potential during long charge-discharge cycles and does not have obvious problems such as fluctuations, short circuits, or failures. The measurement results in Figure 6 clearly demonstrate that the electrolyte prepared in Example 1 has a long sedimentation dissolution lifetime. As can be seen from Figure 7, the resistance R of the solid electrolyte intermediate phase of the Mg / / Mg symmetric half-cell SEI The resistance is 6.2Ω, and the charge transfer resistance R ct The impedance is 23.5Ω. The measurement results in Figure 7 reveal that the reason the electrolyte prepared in Example 1 has a long sedimentation dissolution lifetime is that a stable SEI (Sedimentary Interpolation) is formed on the surface of the metallic magnesium, which has low impedance and can efficiently conduct magnesium ions.

[0091] The measurement results shown in Figures 1 to 7 demonstrate that the electrolyte of this invention can possess excellent electrochemical properties, and at the same time, that the interfacial stability between the electrolyte and the negative electrode is also high.

[0092] To illustrate the potential application of the electrolyte of this invention in magnesium-ion batteries (all batteries), the inventors assembled a magnesium-ion battery using metallic magnesium as the negative electrode, Mo6S8 as the positive electrode, and GF / B as the separator, along with the electrolyte prepared in Example 1, and measured its charge-discharge performance. Figure 8 shows the charge-discharge curve of the first cycle of the magnesium-ion battery, and Figure 9 shows the cycle curve of the magnesium-ion battery. As can be seen from Figure 8, the magnesium-ion battery has a high charge-discharge voltage platform. As can be seen from Figure 9, the magnesium-ion battery has a high discharge capacity (greater than 60 mAh / g) and Coulomb efficiency even at a high current density of 128.8 mA / g, and is capable of stable charge-discharge for more than 800 cycles. The measurement results in Figures 8 and 9 demonstrate that the electrolyte of this invention can be applied to magnesium-ion batteries, and that magnesium-ion batteries can have the advantage of an even longer cyclic life.

[0093] The above describes only specific embodiments of the present application and does not limit the scope of protection. Any person skilled in the art can easily conceive of various equivalent variations or substitutions within the scope of the art disclosed herein, and all such variations or substitutions should fall within the scope of protection. Therefore, the scope of protection of the present application should be in accordance with the claims of the patent.

Claims

1. It contains an electrolyte salt and a non-aqueous solvent, The aforementioned electrolyte salt is [Mg ｘ M ２ｘ－１ P ｙ ] [Mg(OR Ｆ ) ３ Q ｚ ] includes, x represents an integer between 1 and 6. y represents an integer between 1 and 6. z represents an integer between 0 and 6. M represents one or more of the following: F-, Cl-, Br-, I-, HMDS-, CF3SO3-, (CF3SO2)2N-. R Ｆ Each of these independently represents a C1-C6 aliphatic hydrocarbon group that is partially or fully fluorinated, or a C6-C12 aromatic hydrocarbon group that is partially or fully fluorinated. P and Q represent complexing agents. The complexing agent P and the complexing agent Q each independently represent one or more types of ionic liquids and first organic solvents. The aforementioned ionic liquid includes one or more types of imidazole-based ionic liquids, piperidine-based ionic liquids, and pyrrole-based ionic liquids. The first organic solvent is an electrolyte for a magnesium secondary battery, comprising one or more of the following: ether-based solvents, imidazole-based solvents, pyridine-based solvents, sulfone-based solvents, ester-based solvents, aromatic hydrocarbon-based solvents, amide-based solvents, and nitrile-based solvents.

2. The cation of the electrolyte salt is [Mg ｘ M ２ｘ－１ P ｙ ＋ and the anion is [Mg(OR Ｆ ) ３ Q ｚ － The electrolyte according to claim 1.​​

3. M is F － , Cl － , Br － , I － It is one or more of the following types, and / or R Ｆ Each of these independently represents a partially or fully fluorinated C1-C6 alkyl group, phenyl group, C6-C12 alkylphenyl group, or C6-C12 phenylalkyl group, and also represents a partially or fully fluorinated methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, phenyl, methylphenyl, ethylphenyl, n-propylphenyl, t-butylphenyl, phenylmethyl, or phenylethyl, and / or The electrolyte according to claim 1, wherein the non-aqueous solvent represents one or more types from ionic liquids and first organic solvents, and the non-aqueous solvent, the complexing agent P, and the complexing agent Q are the same.

4. The imidazole-based ionic liquid comprises one or more of the following: 1-ethyl-3-methylimidazolium tetrafluoroborate salt, 1-ethyl-3-methylimidazolium hexafluorophosphate salt, and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide salt. The aforementioned pyrrole-based ionic liquid contains an N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide salt, The piperidine-based ionic liquid comprises an N-butyl-N-methylpiperidinium bis(trifluoromethylsulfonyl)imide salt and / or The ether-based solvent includes one or more of the following: dioxolane, tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and polyethylene glycol dimethyl ether. The pyridine-based solvent includes one or more of the following: pyridine, 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, 2,6-dichloropyridine, and 2-aminopyridine. The electrolyte according to claim 1, wherein the ester solvent comprises one or more of ethylene carbonate and ethyl acetate.

5. [Mg in the electrolyte] ｘ M ２ｘ－１ P ｙ ] [Mg(OR Ｆ ) ３ Q ｚ The electrolyte according to claim 1, wherein the concentration of [ ] is 0.1 mol / L to 1.2 mol / L.

6. Mg(OR Ｆ ) ２ , anhydrous MgM ２ and step S100 which provides a non-aqueous solvent, Mg(OR Ｆ ) ２ , anhydrous MgM ２ And after mixing with a non-aqueous solvent, 25 ｏ C to 100 ｏ A method for preparing an electrolyte according to any one of claims 1 to 5, comprising step S200 of reacting with C to obtain an electrolyte.

7. The method according to claim 6, wherein in S200, the reaction time is 3h to 48h.

8. Anhydrous MgM ２ Mg(OR) Ｆ ) ２ The method according to claim 6, wherein the molar ratio is 1:(0.5 to 3.0).

9. Mg(OR Ｆ ) ２ It is obtained by the following preparation method, HOR in the second organic solvent Ｆ and MgR ２ After mixing, 0 ｏ C-200 ｏ The reaction is carried out with C, and the second organic solvent is removed by drying, and Mg(OR Ｆ ) ２ Obtained, MgR ２ It is selected from magnesium methoxide, magnesium ethoxide, magnesium propoxide, dibutylmagnesium, or ethyl magnesium chloride. The method according to claim 6, wherein the second organic solvent includes one or more of the following: ether solvents, imidazole solvents, pyridine solvents, sulfone solvents, ester solvents, aromatic hydrocarbon solvents, amide solvents, and nitrile solvents.

10. A magnesium secondary battery comprising the electrolyte according to any one of claims 1 to 5.

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