A low-temperature rechargeable magnesium battery electrolyte and its preparation method and application

Abstract

The present invention relates to the field of electrochemical technology, and more specifically to a low-temperature rechargeable magnesium battery electrolyte, its preparation method, and its application. The electrolyte comprises a magnesium salt, a strongly coordinating amine solvent, and / or a low-melting-point solvent. The electrolyte remains liquid at temperatures of -100°C and above without significant phase transition, and its ionic conductivity can reach 1.24 mS·cm at -40°C. ‑1 As above, the oxidation stability potential can reach above 4.37V, and the average coulombic efficiency of 1000 cycles can reach 99.74%, that is, it still has high oxidation stability and good cyclability at low temperatures; in addition, the electrolyte is prepared by mixing and stirring a magnesium salt, a strongly coordinating amine solvent and / or a low-melting-point solvent at room temperature, and the preparation method is simple.

Description

Technical Field

[0001] The present invention relates to the field of electrochemical technology, and in particular to a low-temperature rechargeable magnesium battery electrolyte, a preparation method thereof, and an application thereof. Background Art

[0002] As one of the advanced energy storage technologies, lithium-ion batteries have the advantages of high energy density, stable working potential, long service life, and low self-discharge rate. However, problems such as lithium resource shortage, poor safety, and dendrites are still difficult to solve. In contrast, magnesium resources are abundant, and the abundance in the earth's crust is more than a thousand times that of lithium resources. This provides resource guarantees for the development of rechargeable magnesium batteries. In addition, the metallic magnesium negative electrode has a high theoretical specific capacity (2205mAh g -1 、3833mAh·cm -3 ), not prone to dendrite formation and low cost, making magnesium batteries one of the potential competitors to solve the bottleneck problem of lithium batteries.

[0003] With the continuous growth of energy storage demand and the continuous expansion of various battery application scenarios, most power-consuming products (such as portable electronic products, aircraft, electric vehicles, control systems, high-altitude drones or submarines, etc.) have increasingly higher requirements for batteries to adapt to extreme low-temperature weather. Therefore, expanding the low-temperature operating range of magnesium batteries is of great significance to improving low-temperature electrochemical performance. Rechargeable magnesium battery electrolyte, as the blood of magnesium batteries, runs through the entire development process of magnesium batteries and becomes an important factor in determining whether magnesium batteries can operate stably at low temperatures.

[0004] However, there is currently a lack of research on low-temperature magnesium salt electrolytes for magnesium batteries, and the following problems still exist in low-temperature rechargeable magnesium battery electrolytes: First, the electrolyte has low solubility at low temperatures and is prone to salting out, resulting in a low magnesium ion concentration; second, the magnesium ion transport kinetics is affected by temperature. Generally, the lower the temperature, the slower the ion transport kinetics; third, the electrolyte and electrode interface is unstable at low temperatures and cannot work stably for a long time. In addition, the magnesium negative electrode is easily passivated, and it is impossible to maintain a small polarization voltage and high oxidation stability to obtain high capacity performance. Summary of the Invention

[0005] To address the above issues, the present invention aims to provide a low-temperature rechargeable magnesium battery electrolyte, a preparation method thereof, and a low-temperature rechargeable magnesium battery prepared using the electrolyte. The low-temperature rechargeable magnesium battery electrolyte is prepared from a magnesium salt, a strongly coordinating amine solvent, and / or a low-melting-point solvent. The prepared low-temperature rechargeable magnesium battery electrolyte exhibits high ionic conductivity, high oxidative stability, and good cycling performance at temperatures as low as -60°C, enabling stable operation at relatively low temperatures.

[0006] In order to achieve the above object, the present invention can adopt the following technical solutions:

[0007] One aspect of the present invention provides a low-temperature rechargeable magnesium battery electrolyte, which includes a magnesium salt and a strongly coordinating amine solvent.

[0008] It should be noted that in the present invention, by dissolving the magnesium salt in a strongly coordinating amine solvent, low-temperature reversible deposition and dissolution can be achieved, and the solubility of the electrolyte is increased, thereby achieving low-temperature reversible deposition and dissolution.

[0009] Preferably, the magnesium salt can be selected from one or more combinations of magnesium bis(trifluoromethanesulfonyl)imide (Mg(TFSI)2) and magnesium trifluoromethanesulfonate (Mg(CF3SO3)2). It should be noted that the above-mentioned strongly coordinating amine solvents have good compatibility with magnesium salt electrolytes, especially sulfonic acid magnesium salts.

[0010] Preferably, the above-mentioned strong coordinating amine solvent can be selected from 2-methoxyethylamine, N-methyl-2-methoxyethylamine, 3-methoxypropylamine, 1-methoxy-2-propylamine, 2-ethoxyethylamine, 2-(2-methoxyethoxy)ethylamine, N-tert-butyl-2-methoxyethylamine, N-(2-methoxyethyl)-N-propylamine, N-(2-methoxyethyl)methylamine, 2-aminoethyl isopropyl ether, bis(2-methoxyethyl)amine, N-(2-methoxy)methylamine, bis(2-isopropoxyethyl)amine or 2,2'-oxybis(ethylamine). It should be noted that when the above-mentioned strong coordinating amine solvent is used in the electrolyte of the present invention, the performance of the prepared electrolyte is better than that of other strong coordinating amine solvents.

[0011] Preferably, the low-temperature rechargeable magnesium battery electrolyte may further include a low-melting-point solvent. It should be noted that the purpose of the "low-melting-point solvent" in the present invention is to prevent the dissolved magnesium salt from solidifying at low temperatures. Therefore, the "low-melting-point solvent" can be selected according to the required operating temperature, preferably a solvent with a melting point below -40°C or below -60°C.

[0012] Preferably, the low melting point solvent can be selected from ether solvents. Specifically, ether solvents have good chemical stability, low melting point and high dielectric constant, which can provide the electrolyte with the required low temperature stability.

[0013] Preferably, the ether solvent can be selected from one or more of 4-aminotetrahydropyran, 3-methyloxazolidine, 2,6-dimethylmorpholine, tetrahydrothiophene, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, dimethoxymethane, 1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, 4-methyl-1,3-dioxane or tetrahydropyran.

[0014] Preferably, the volume proportion of the above-mentioned low melting point solvent can be 0<v(%)≤90%. Specifically, the volume proportion of the low melting point solvent can be 5%, 10%, 15%, 20%, 25%, 50%, 60%, 70% or 80%, etc. It should be noted that the volume proportion in the present invention refers to the volume proportion of the total volume of the strong coordinating amine solvent and the low melting point solvent. For example, when the volume proportion of the low melting point solvent is 10%, it means that in the total volume of the low melting point solvent and the strong coordinating amine solvent, the volume proportion of the low melting point solvent is 10%, and the volume proportion of the strong coordinating amine solvent is 90%.

[0015] Preferably, the total amount of the low melting point ether solvent and the strongly coordinating amine solvent added should be sufficient to achieve a molar concentration of the magnesium salt of 0.1 mol / L-1.0 mol / L.

[0016] It should be noted that in order to allow the magnesium salt to fully react in the two solvents, the molar concentration of the magnesium salt in the two solvents may preferably be 0.1 mol / L-1.0 mol / L. When the molar concentration of the magnesium salt is lower than 0.1 mol / L, the magnesium salt content is low and the ionic conductivity is low; when the molar concentration of the magnesium salt is greater than 1.0 mol / L, the viscosity of the electrolyte increases and the reaction rate decreases.

[0017] It should also be noted that the low-temperature rechargeable magnesium battery electrolyte of the present invention not only has the advantages of high oxidation stability and good circulation at temperatures as low as -60°C, but also has low temperature working stability. In addition, the raw materials for its preparation do not contain chlorine, thereby avoiding chlorine corrosion of the current collector during use.

[0018] Another aspect of the present invention provides a method for preparing the low-temperature rechargeable magnesium battery electrolyte of the present invention, which comprises mixing a magnesium salt, a low-melting-point ether solvent and a strongly coordinating amine solvent, and stirring to prepare the low-temperature rechargeable magnesium battery electrolyte.

[0019] It should be understood that the mixing and stirring in the above preparation method are conventional operations in the art. Furthermore, it should be noted that in the present invention, the magnesium salt, low melting point solvent, and strongly coordinating amine solvent can be mixed at room temperature, without requiring harsh mixing conditions, which facilitates the scale-up of production of the low-temperature rechargeable magnesium battery electrolyte of the present invention.

[0020] It should be noted that when preparing an electrolyte without a low-melting-point solvent, the method is the same as that of the electrolyte containing a low-melting-point solvent, that is, the magnesium salt and the strong coordinating amine solvent are mixed and stirred to prepare the electrolyte.

[0021] Preferably, the above reaction can be carried out under an inert atmosphere with a water and oxygen content of less than 0.01 ppm. Specifically, in order to prevent the raw materials from reacting with oxygen and water during the reaction, the raw materials can be placed under an inert atmosphere and in an environment with a water and oxygen content of less than 0.01 ppm for the reaction.

[0022] Preferably, the stirring comprises reacting by magnetic stirring for 12h-24h. It should be noted that the purpose of stirring in the present invention is to make the mixing more complete, and the stirring method can be selected from those known in the art, such as stirring with a stirrer, or using magnetic stirring, etc.; in the present invention, magnetic stirring is preferably used for 12h-24h, such as 15h, 17h, 19h, 21h or 23h, etc.; if the stirring time is less than 12h, the reaction is not complete, and if the stirring time is greater than 24h, unnecessary energy loss is generated when the reaction is already very sufficient.

[0023] Preferably, the preparation method further comprises pre-treating the low melting point solvent and the strong coordinating amine solvent respectively, wherein the pre-treating method comprises: mixing the low melting point solvent or the strong coordinating amine solvent with sodium, redistilling the solvent under an inert atmosphere, adding the solvent activated at a temperature of 300°C to 400°C, Type molecular sieve, sealed and stored in an inert atmosphere to ensure an oxygen-free and water-free environment.

[0024] Another aspect of the present invention provides a low-temperature rechargeable magnesium battery, which includes the low-temperature rechargeable magnesium battery electrolyte of the present invention.

[0025] Specifically, the low-temperature rechargeable magnesium battery electrolyte of the present invention, combined with a magnesium battery positive electrode material and a negative electrode material, can be assembled into a battery, and the assembled battery has excellent electrical performance. It should be noted that the magnesium battery positive electrode material is a material known in the art, and the negative electrode material is a material known in the art, such as magnesium foil or a magnesium alloy.

[0026] The beneficial effects of the present invention include at least:

[0027] (1) The low-temperature rechargeable magnesium battery electrolyte provided by the present invention remains liquid at -100°C and above without obvious phase change;

[0028] (2) The low-temperature rechargeable magnesium battery electrolyte provided by the present invention has an oxidation stability potential greater than 4V on stainless steel at a temperature of -40°C, and the electrolyte has good oxidation stability;

[0029] (3) The low-temperature rechargeable magnesium battery electrolyte provided by the present invention uses stainless steel as the working electrode. At a temperature of -20°C, the first cycle dissolution current density of the electrolyte is 2.43 mA·cm -2 At -40°C, the first cycle dissolution current density of the electrolyte is 0.40 mA cm-2 ; That is, the electrolyte can reversely deposit and dissolve at -20℃ and -40℃;

[0030] (4) The low-temperature rechargeable magnesium battery electrolyte provided by the present invention uses stainless steel as the working electrode. At -40°C, the coulombic efficiency of magnesium reversible deposition and dissolution gradually increases, reaching 92.16% in the first cycle and an average coulombic efficiency of 99.77% after 1800 stable cycles.

[0031] (5) The Mg / Mg symmetrical battery assembled with the low-temperature rechargeable magnesium battery electrolyte provided by the present invention has a current density of 0.5 mA·cm at -40°C. -2 When the battery is stably cycled for 600 hours, the polarization potential does not increase significantly, and the overpotential is low at 347mV; that is, the electrolyte still has excellent stability for the magnesium negative electrode even at low temperatures;

[0032] (6) The low-temperature rechargeable magnesium battery electrolyte provided by the present invention has a gradually increasing coulombic efficiency of magnesium reversible deposition and dissolution on a stainless steel substrate at -60°C. The coulombic efficiency of the first cycle reaches 90.49%, which increases to 98.17% after 10 cycles, and the average coulombic efficiency after 120 cycles is 98.97%;

[0033] (7) The low-temperature rechargeable magnesium battery electrolyte provided by the present invention has an ionic conductivity of 1.24 mS·cm at -40°C. -1 Above, the oxidation stability potential can reach above 4.37V, and the average coulombic efficiency of 1000 cycles can reach 99.74%, that is, the electrolyte still has high oxidation stability and good cyclability at low temperatures and can still work normally;

[0034] (8) The low-temperature rechargeable magnesium battery electrolyte provided by the present invention is prepared by mixing and stirring a magnesium salt, a strongly coordinating amine solvent and / or a low melting point solvent at room temperature. The preparation method is simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The differential scanning calorimetry curves of the electrolytes prepared in Examples 1 to 6 of the present invention are shown;

[0036] Figure 2 The linear sweep voltammetry curve of the electrolyte prepared in Example 1 of the present invention at -40°C with stainless steel foil as the working electrode;

[0037] Figure 3 Cyclic voltammetry curve of the electrolyte prepared in Example 1 of the present invention at -20°C with stainless steel foil as the working electrode;

[0038] Figure 4The cyclic voltammetry curve of the electrolyte prepared in Example 1 of the present invention at -40°C with stainless steel foil as the working electrode;

[0039] Figure 5 The electrolyte prepared in Example 1 of the present invention uses stainless steel foil as the working electrode at 0.5 mA·cm -2 Coulombic efficiency of reversible magnesium deposition / dissolution at -40°C under current density;

[0040] Figure 6 Polarization performance curves of the Mg / Mg symmetrical battery assembled with the electrolyte prepared in Example 1 of the present invention at -40°C at different current densities;

[0041] Figure 7 The electrolyte prepared in Example 1 of the present invention uses stainless steel foil as the working electrode at 0.5 mA·cm -2 Coulombic efficiency of reversible magnesium deposition / dissolution at -60°C under current density;

[0042] Figure 8 The electrolyte prepared in Example 2 of the present invention uses stainless steel foil as the working electrode at 0.5 mA·cm -2 Coulombic efficiency of reversible magnesium deposition / dissolution at -40°C under current density;

[0043] Figure 9 The electrolyte prepared in Example 3 of the present invention uses stainless steel foil as the working electrode at 0.5 mA·cm -2 Coulombic efficiency of reversible magnesium deposition / dissolution at -40°C under current density;

[0044] Figure 10 The electrolyte prepared in Example 4 of the present invention uses stainless steel foil as the working electrode at 0.5 mA·cm -2 Coulombic efficiency of reversible magnesium deposition / dissolution at -40°C under current density;

[0045] Figure 11 The electrolyte prepared in Example 5 of the present invention uses stainless steel foil as the working electrode at 0.5 mA·cm -2 Coulombic efficiency of reversible magnesium deposition / dissolution at -40°C under current density;

[0046] Figure 12 The electrolyte prepared in Example 6 of the present invention uses stainless steel foil as the working electrode at 0.5 mA·cm -2 Coulombic efficiency of reversible magnesium deposition / dissolution at -40°C under current density;

[0047] Figure 13 The electrolyte prepared in Example 7 of the present invention uses stainless steel foil as the working electrode at 0.5 mA·cm -2Coulombic efficiency of reversible magnesium deposition / dissolution at -20°C under different current densities. DETAILED DESCRIPTION

[0048] The examples are provided to better illustrate the present invention, but are not intended to limit the present invention to the examples. Therefore, non-essential improvements and adjustments to the embodiments made by those skilled in the art based on the above-mentioned invention still fall within the scope of protection of the present invention.

[0049] The terms used herein are only used to describe specific embodiments and are not intended to limit the present disclosure. Unless the context has a significantly different meaning, expressions in the singular include expressions in the plural. As used herein, it should be understood that terms such as "include", "have", "comprise" and the like are intended to indicate the presence of features, numbers, operations, components, parts, elements, materials or combinations. The terms of the present invention are disclosed in the specification and are not intended to exclude the possibility that one or more other features, numbers, operations, components, parts, elements, materials or combinations thereof may exist or may be added. As used herein, " / " may be interpreted as "and" or "or", depending on the circumstances.

[0050] In order to better understand the present invention, the content of the present invention is further explained below with reference to specific examples, but the content of the present invention is not limited to the following examples.

[0051] 1. Preparation of electrolyte

[0052] Example 1

[0053] 0.9673 g of Mg(CF3SO3)2 was dissolved in a reagent bottle containing 5 mL of dried 1,3-dioxolane, and then 1 mL of 2-methoxyethylamine was slowly added. The above solution was stirred at 400 r / min at 25°C for 12 hours to obtain an electrolyte.

[0054] In addition, 1,3-dioxolane and 2-methoxyethylamine were pretreated before use, specifically including: adding 50 mL of 1,3-dioxolane or 2-methoxyethylamine to a container, adding 1.5 g of sodium metal, redistilling under an inert atmosphere, adding the distilled solvent that had been activated at 350 ° C for 15 h, Type molecular sieve, sealed and stored under inert atmosphere.

[0055] In addition, all operation steps were carried out in a glove box filled with argon, and the concentrations of water and oxygen were less than 0.01 ppm at room temperature.

[0056] Example 1 to Example 7

[0057] Different electrolytes were prepared according to the electrolyte preparation raw materials shown in Table 1 below and the preparation method in Example 7.

[0058] Table 1 Raw materials for preparing electrolytes of Examples 1 to 7

[0059] Example magnesium salts Ether solvents Strongly coordinating amine solvents Example 1 <![CDATA[0.9673gMg(CF3SO3)2]]> 5mL1,3-dioxolane 1 mL 2-methoxyethylamine Example 2 <![CDATA[0.9673gMg(CF3SO3)2]]> 5mL ethylene glycol dimethyl ether 1 mL 2-methoxyethylamine Example 3 <![CDATA[0.9673gMg(CF3SO3)2]]> 5 mL tetrahydrofuran 1 mL 2-methoxyethylamine Example 4 <![CDATA[0.9673gMg(CF3SO3)2]]> 5mL1,3-dioxane 1 mL 2-methoxyethylamine Example 5 <![CDATA[1.7537gMg(TFSI)2]]> 5mL1,3-dioxolane 1mL 2-ethoxyethylamine Example 6 <![CDATA[1.7537gMg(TFSI)2]]> 5 mL tetrahydrofuran 1mL 3-methoxypropylamine Example 7 <![CDATA[0.1612gMg(CF3SO3)2]]> - 1 mL 2-methoxyethylamine

[0060] 2. Electrolyte performance test

[0061] In the embodiment of the present invention, the reversible magnesium deposition and dissolution performance and oxidation stability of the electrolyte are tested by cyclic voltammetry and linear sweep voltammetry, respectively. Specifically, a two-electrode system is adopted, with a magnesium sheet (12 mm) electrode as the reference electrode and counter electrode, and a stainless steel foil (SS) current collector (16 mm) electrode as the working electrode; wherein, for cyclic voltammetry, the potential range during the test is -1 V to 2 V, the sweep rate is 25 mV / s, and the scan is scanned from the negative direction of the open circuit voltage; for linear sweep voltammetry, the potential range during the test is from the open circuit voltage to 5.5 V, the sweep rate is 1 mV / s, and the test temperature is -20 ° C, -40 ° C and -60 ° C; in addition, all electrodes are washed alternately with ethanol and deionized water three times in sequence to thoroughly remove impurities on the entire electrode surface; the cleaned electrodes are vacuum dried for 12 hours and placed in a glove box for standby use.

[0062] In the embodiment of the present invention, the coulombic efficiency and charge-discharge characteristics of magnesium in the electrolyte are tested by assembling a CR2032 button cell for constant current charge-discharge testing. Specifically, the test includes: assembling in an inert atmosphere glove box, with the water and oxygen content less than 0.01ppm; the working electrode is polished stainless steel foil (SS), and the counter electrode and reference electrode are polished magnesium sheets; the diaphragm is a GF / A membrane; and the battery is assembled together with the electrolyte of the present invention to form a CR2032 button cell; after the battery is assembled, it is allowed to stand at room temperature for 12 hours before measurement; the entire test process is carried out on a Xinwei charge-discharge test system; wherein, during discharge, the electrochemical deposition reaction of magnesium occurs on the working electrode, and the current density is 0.1mA·cm -2 -1.0mA·cm -2 , using time control (discharge for 1 hour); the charging process corresponds to the dissolution reaction of magnesium deposited on the working electrode, with a current density of 0.1 mA cm -2 -1.0mA·cm -2 , using voltage control (charged to 1.2V vs.Mg RE).

[0063] In the embodiment of the present invention, the cycling and rate polarization performance of magnesium in the electrolyte were tested by assembling CR2032 button cells for constant current charge and discharge testing. Specifically, the test included: assembling in an inert atmosphere glove box with water and oxygen contents less than 0.01 ppm; using polished magnesium sheets (12 mm) for the counter and reference electrodes, and GF / A membrane for the diaphragm, and assembling them together with a homemade electrolyte to form a CR2032 button cell; after the battery was assembled, it was allowed to stand at room temperature for 12 hours before measurement; the entire test process was carried out on a Xinwei charge and discharge test system; during discharge, the electrochemical deposition reaction of magnesium occurred on the working electrode, with a current density of 0.1 mA cm -2 -3.0mA·cm -2 , using time control (discharge 30min); the charging process corresponds to the dissolution reaction of magnesium deposited on the working electrode, with a current density of 0.1mA·cm -2 -3.0mA·cm -2 , using time control (charging 30min).

[0064] (1) Differential Scanning Calorimetry (DSC)

[0065] Differential scanning calorimetry (DSC) was performed on the electrolytes prepared in Examples 1 to 3 above; the test conditions were as follows:

[0066] ① Cool down from 25℃ to -100℃, with a cooling rate of 1℃ / min; ② Keep at -100℃ for 5 minutes; ③ Heat up from -100℃ to 60℃, with a heating rate of 5℃ / min. Figure 1 As shown, the results show that the electrolyte can remain liquid at -100°C without obvious phase change, which makes it possible for the electrolyte to work at low temperatures.

[0067] (2) Oxidation stability potential at -40°C (vs. Mg / Mg 2+ )

[0068] The electrolyte prepared in Example 1 was tested on a stainless steel working electrode using the above test method to measure the oxidation stability potential (vs. Mg / Mg) at -40°C. 2+ ) test, the test results are as follows Figure 2 As shown, the results show that the oxidation stability potential of the electrolyte prepared in Example 1 on SS at -40°C is greater than 4V. This result shows that the electrolyte has good oxidation stability and can meet the matching requirements of most positive electrode materials.

[0069] (3) Reversible magnesium deposition and dissolution performance at -20°C and -40°C

[0070] The above test method was used to test the reversible magnesium deposition and dissolution performance of the electrolyte prepared in Example 1 on a stainless steel working electrode at -20°C and -40°C. The test results are as follows: Figure 3 and Figure 4 As shown in the results, with stainless steel SS as the working electrode, at -20°C, the first cycle dissolution current density of the electrolyte prepared by the present invention is 2.43 mA·cm -2 At -40°C, the first cycle dissolution current density of the electrolyte prepared by the present invention is 0.40 mA·cm -2 ; The results show that the electrolyte can reversibly deposit and dissolve at -20℃ and -40℃.

[0071] (4) Coulombic efficiency test at -40℃

[0072] The coulombic efficiency test of the electrolyte prepared in Example 1 was carried out on a stainless steel working electrode at -40°C using the above test method. The test results are as follows: Figure 5 As shown, the results show that the coulombic efficiency of reversible deposition and dissolution of magnesium in the electrolyte prepared in Example 1 (on a stainless steel substrate) gradually increases, the coulombic efficiency of the first cycle reaches 92.16%, and the average coulombic efficiency after 1800 stable cycles is 99.77%.

[0073] (5) Polarization performance test at -40℃

[0074] The polarization performance of the symmetrical metal battery Mg / Mg assembled with the electrolyte prepared in Example 1 was tested at -40°C using the above test method. The test results are as follows: Figure 6 As shown in the results, the current density is 0.5mA·cm -2 The battery cycled stably for 600 hours with no significant increase in polarization potential and a low overpotential of 347 mV. The results show that the electrolyte has excellent stability for magnesium.

[0075] (6) Coulombic efficiency test at -60℃

[0076] The electrolytes prepared in Examples 1 to 7 were tested for coulombic efficiency at -60°C on a stainless steel working electrode using the above test method. The test results of the electrolyte prepared in Example 1 are as follows: Figure 7 As shown, the results show that the coulombic efficiency of reversible deposition and dissolution of magnesium in the electrolyte prepared in Example 1 (on a stainless steel substrate) gradually increases, with the coulombic efficiency in the first cycle reaching 90.49%, increasing to 98.17% after 10 cycles, and the average coulombic efficiency after 120 cycles being 98.97%.

[0077] The test results of the electrolytes prepared in Examples 2 to 7 are as follows: Figure 8 、 Figure 9 、 Figure 10、 Figure 11 、 Figure 12 and Figure 13 shown.

[0078] (7) Electrochemical performance test at -40℃

[0079] The electrochemical performance of the electrolytes prepared in Examples 1 to 6 was tested at -40°C using the linear sweep and constant current charge-discharge test methods. The results are shown in Table 2.

[0080] Table 2 Electrochemical performance of the electrolytes prepared in Examples 1 to 6 at -40°C

[0081]

[0082] It can be seen from Table 2 above that the electrolytes prepared in the present invention still have good electrochemical properties at -40°C and can work stably at low temperatures.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should all be covered by the scope of the claims of the present invention.

Claims

1. Application of a rechargeable magnesium battery electrolyte in the preparation of a low-temperature resistant battery, the rechargeable magnesium battery electrolyte comprising a magnesium salt, a strongly coordinating amine solvent and a low melting point solvent; the operating temperature of the low-temperature resistant battery is as low as -60°C; the total amount of the low melting point solvent and the strongly coordinating amine solvent added satisfies the molar concentration of the magnesium salt of 0.1 mol / L-1.0 mol / L; the magnesium salt is selected from one or more combinations of magnesium bis(trifluoromethanesulfonyl)imide and magnesium trifluoromethanesulfonate; the strongly coordinating amine solvent is selected from 2-methoxyethylamine, N-methyl-2-methoxyethylamine, 3-methoxypropylamine, 1-methoxy-2-propylamine, 2-ethoxyethylamine, 2-(2-methoxyethoxy)ethylamine, N-tert-butyl-2-methoxyethylamine, At least one of N-(2-methoxyethyl)-N-propylamine, N-(2-methoxyethyl)methylamine, 2-aminoethyl isopropyl ether, bis(2-methoxyethyl)amine, N-(2-methoxy)methylamine, bis(2-isopropoxyethyl)amine or 2,2'-oxybis(ethylamine); the low melting point solvent is selected from ether solvents, and the ether solvent is selected from at least one of 4-aminotetrahydropyran, 3-methyloxazolidine, 2,6-dimethylmorpholine, tetrahydrothiophene, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, dimethoxymethane, 1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, 4-methyl-1,3-dioxane or monooxane.

2. The use according to claim 1, characterized in that The volume proportion of the low melting point solvent is 0<v(%)≤90%.

3. The use according to claim 1 or 2, characterized in that The preparation method of the rechargeable magnesium battery electrolyte comprises the steps of mixing a magnesium salt, a low melting point solvent and a strong coordinating amine solvent, and stirring the mixture to obtain the low-temperature rechargeable magnesium battery electrolyte.

4. The use according to claim 3, characterized in that The stirring includes magnetic stirring for 12 hours to 24 hours; and / or the entire process is carried out under an inert atmosphere, and the water and oxygen content is less than 0.01 ppm.

5. The use according to claim 3, characterized in that The preparation method also includes pretreating the low melting point solvent and the strongly coordinating amine solvent respectively. The pretreatment method includes: mixing the low melting point solvent or the strongly coordinating amine solvent with sodium, redistilling under an inert atmosphere, adding 4A molecular sieve activated at a high temperature of 300°C-400°C to the distilled solvent, sealing and storing under an inert atmosphere.

6. A low-temperature rechargeable magnesium battery electrolyte, characterized in that: The invention comprises a magnesium salt, a strongly coordinating amine solvent and a low melting point solvent; the magnesium salt is selected from magnesium trifluoromethanesulfonate, the strongly coordinating amine solvent is selected from 2-methoxyethylamine, and the low melting point solvent is selected from 1,3-dioxolane or 1,3-dioxane; the total amount of the low melting point solvent and the strongly coordinating amine solvent added satisfies the molar concentration of the magnesium salt of 0.1 mol / L-1.0 mol / L; the operating temperature of the low-temperature rechargeable magnesium battery electrolyte is as low as -60°C.

7. The low-temperature rechargeable magnesium battery electrolyte according to claim 6, characterized in that: The volume proportion of the low melting point solvent is 0<v(%)≤90%.

8. The method for preparing a low-temperature rechargeable magnesium battery electrolyte according to any one of claims 6 to 7, characterized in that: The method comprises the steps of mixing and stirring a magnesium salt, a low melting point solvent and a strong coordinating amine solvent to prepare a low temperature rechargeable magnesium battery electrolyte.

9. The method for preparing a low-temperature rechargeable magnesium battery electrolyte according to claim 8, characterized in that: The stirring includes magnetic stirring for 12 hours to 24 hours; and / or the entire process is carried out under an inert atmosphere, and the water and oxygen content is less than 0.01 ppm.

10. The method for preparing a low-temperature rechargeable magnesium battery electrolyte according to claim 8 or 9, characterized in that: The preparation method also includes pretreating the low melting point solvent and the strongly coordinating amine solvent respectively. The pretreatment method includes: mixing the low melting point solvent or the strongly coordinating amine solvent with sodium, redistilling under an inert atmosphere, adding 4A molecular sieve activated at a high temperature of 300°C-400°C to the distilled solvent, sealing and storing under an inert atmosphere.

11. Low-temperature rechargeable magnesium battery, characterized in that: The invention comprises the low-temperature rechargeable magnesium battery electrolyte according to any one of claims 6 to 7.

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