A high-stability boron-based magnesium salt and its efficient and large-scale preparation method and application

Abstract

The invention relates to the technical field of magnesium ion batteries, and discloses a high-stability boron-based magnesium salt and an efficient and large-scale preparation method and application thereof. The invention adopts a simple and efficient anion replacement method. The boron-based magnesium salt is quickly prepared by reacting a boron source with a magnesium source to generate a borohydride and an alcohol source, with a yield of 79-96%. The product has good stability to air and water, high purity, good conductivity, and no other metal cations and chloride ions are introduced. The entire process is short, clean and environmentally friendly, safe and reliable, efficient and low in energy consumption, and has industrial prospects. Compared with the existing two-step preparation method, the preparation efficiency is increased by more than 80%; compared with the direct use of magnesium borohydride raw materials, the cost can be reduced by up to 93%.

Description

Technical Field

[0001] The present invention belongs to the technical field of magnesium ion batteries, and in particular relates to a high-stability boron-based magnesium salt and an efficient and large-scale preparation method and application thereof. Background Art

[0002] As energy storage technology develops, the demand for higher energy density storage is driving research beyond the currently dominant lithium-ion batteries. + It is an effective way to achieve high energy density commercial rechargeable batteries. Magnesium (Mg) metal has abundant reserves (ranked 8th among elements in the earth's crust), low reduction potential (-2.356Vvs.SHE), is not easy to form dendrites, and has a high volume energy density (3833mAh / cm 3 ) and other advantages, it has been regarded as one of the most promising new energy storage technologies.

[0003] However, the lack of suitable electrolytes remains a key challenge in building rechargeable magnesium batteries with high energy density. 2+ Coordination with the ether oxygen group of the ether solvent and compounds with large steric volume and weakly coordinated anions realizes reversible electrochemistry. Among them, the performance of boron-based magnesium salts is particularly outstanding, especially Mg[B(Ohfip)4)2 has high oxidation stability (~4V vs.Mg), high ionic conductivity and excellent Mg deposition coulombic efficiency, which makes it a kind of chlorine-free magnesium electrolyte with great application prospects. At present, boron-based magnesium salts for magnesium batteries are prepared by a two-step method or a replacement method in an argon atmosphere glove box. However, the above method has problems such as high cost of raw materials, complex equipment required for the reaction, harsh reaction conditions, high energy consumption, long time, low yield and high humidity sensitivity, which are not suitable for large-scale production. Therefore, it is crucial to develop a simple, efficient and large-scale preparation method of boron-based magnesium salts to meet the needs of mass production of high-quality boron-based magnesium salts for magnesium batteries.

[0004] Chinese patent application number 202310041131.3 discloses a method for preparing boron-based magnesium salts. It directly uses magnesium borohydride as a raw material, which is expensive, easy to explode, contains impurities such as chloride ions, and easily generates by-products; and the preparation process needs to be carried out in a glove box, which is difficult to control the temperature, has a low yield, and is not suitable for large-scale production.

[0005] Japanese patent publication number JP2021178801A discloses a method for preparing a boron-based magnesium salt. It adopts a two-step synthesis method, first synthesizing Mg(Ohfip)2 magnesium salt, and then further reacting with B(Ohfip)3 boron salt generated by boron source and alcohol source to prepare magnesium borate salt. The preparation process is complicated, time-consuming, highly moisture-sensitive, and the preparation process needs to be carried out in a glove box, which is difficult to control temperature and is not suitable for large-scale production. Summary of the invention

[0006] The invention aims to solve the problems that the existing boron-based magnesium salt synthesis has high raw material cost, long time, low yield and is difficult to meet the requirements of large-scale industrial production. The invention provides a new method for preparing boron-based magnesium salt. The invention adopts a simple and efficient anion replacement method, generates borohydride in situ during the reaction process to prepare the boron-based magnesium salt, does not require the introduction of other metal cations and chloride ions, has high yield and purity, and has excellent product performance.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] The present invention provides a method for efficiently and scalably preparing a high-stability boron-based magnesium salt, comprising the following steps:

[0009] Step 1: reacting a boron source and a magnesium source in an organic solvent to obtain a first reaction system;

[0010] Step 2: reacting the first reaction system with an alcohol source to obtain a second reaction system;

[0011] Step 3: Add a poor solvent to the second reaction system, wash the obtained precipitate, distill under reduced pressure and dry to obtain the boron-based magnesium salt.

[0012] Preferably, the organic solvent includes a non-polar solvent or an ether solvent; the non-polar solvent includes one or more of toluene, hexane, petroleum ether, pentane, dimethylpentane, isooctane and heptane; the ether solvent includes one or more of sulfide, tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether.

[0013] Preferably, the boron source includes borane and / or a borane complex; the borane complex includes one or more of dimethyl sulfide borane, borane triethylamine, borane tetrahydrofuran, borane ammonia complex, N,N-dimethylaniline borane and 1,2-diaryl-o-carborane.

[0014] Preferably, the magnesium source includes magnesium dihydride and / or an alkyl magnesium salt; the alkyl magnesium salt includes one or more of diethyl magnesium, di-n-butyl magnesium, di-sec-butyl magnesium, dibutyl (isopropyl) magnesium, di-n-butyl ethyl magnesium and n-butyl sec-butyl magnesium.

[0015] Preferably, the alcohol source includes monohydric alcohol compounds and / or polyhydric alcohol compounds; the monohydric alcohol compounds include ethanol, difluoroethanol, trifluoroethanol, 1-phenyl-2,2,2-trifluoroethanol, isopropanol, 1,3-dibromo-2-propanol, 2-phenylisopropanol, trifluoropropanol, trifluoroisopropanol, hexafluoroisopropanol, perfluoro-tert-butyl alcohol, 2-trifluoromethyl-2-propanol, 3-perfluorobutyl propanol, 1,1,1,3,3,3 -hexafluoro-2-phenyl-2-propanol, 2,2-bis(trifluoromethyl)propanol, tetrahydropyran-4-ol and tetrahydrofuran methanol; the polyol compound includes one or more of ethylene glycol, 2,3-butanediol, 2,3-diphenyl-2,3-butanediol, 2,3-dimethyl-2,3-butanediol, 1,2,4-butanetriol and hexafluoro-2,3-bis(trifluoromethyl)-2,3-butanediol.

[0016] Preferably, the amount ratio of the boron source to the organic solvent is 1 mmol: 0.5-2.5 mL;

[0017] The magnesium source and the organic solvent are used in a ratio of 1 mmol: 1.0 to 6.0 mL;

[0018] The molar ratio of the boron source to the magnesium source is 1.5-4.0:1.0;

[0019] The molar ratio of the magnesium source to the alcohol source is 1.0:8.5-12.5.

[0020] Preferably, the reaction temperature of step 1 is -5 to 110°C, the reaction time is 5 to 180 min, and the pressure is 0 to 15 MPa;

[0021] The reaction temperature of step 2 is -5 to 110° C., the reaction time is 5 to 120 min, and the pressure is 0 to 15 MPa.

[0022] Preferably, the poor solvent comprises one or more of toluene, n-hexane, cyclohexane, petroleum ether, n-pentane, isopentane, dimethylpentane, cyclopentane, isooctane and heptane;

[0023] The volume ratio of the second reaction system to the poor solvent is 1:0.5-2;

[0024] The temperature of the reduced pressure distillation is 30-60°C and the time is 5-180min;

[0025] The drying includes vacuum drying and / or forced air drying; the drying temperature is 50 to 90° C. and the drying time is 2 to 24 hours.

[0026] The present invention also provides a high-stability boron-based magnesium salt prepared by the method described in the above technical solution.

[0027] The present invention also provides the use of the high-stability boron-based magnesium salt described in the above technical solution in a magnesium battery electrolyte.

[0028] The invention provides a method for efficiently and massively preparing a high-stability boron-based magnesium salt, comprising the following steps: step 1: reacting a boron source and a magnesium source in an organic solvent to obtain a first reaction system; step 2: reacting the first reaction system with an alcohol source to obtain a second reaction system; and step 3: adding a poor solvent to the second reaction system, washing the obtained precipitate, distilling under reduced pressure and drying to obtain the boron-based magnesium salt.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The present invention adopts anion replacement method, generates borohydride in situ during the synthesis process, and then reacts with an alcohol source to quickly prepare boron-based magnesium salt. The preparation process is simple and efficient, no other metal cations and chloride ions are introduced, the raw material cost is low, and large-scale production can be achieved with a yield of 79-96%. The preparation efficiency can be increased by more than 80% compared with the existing two-step method, and the cost can be reduced by up to 93% compared with the direct use of magnesium borohydride raw materials. The prepared magnesium borate salt has good air and water stability, high yield, high purity, and high conductivity. In addition, the entire process is safe, efficient, clean, environmentally friendly, and low energy consumption is suitable for industrial large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a SEM image of the intermediate product borohydride in the preparation process of argon atmosphere in Example 1;

[0032] Figure 2 The XRD spectrum of the intermediate product borohydride in the preparation process of argon atmosphere in Example 1;

[0033] Figure 3 This is a SEM image of magnesium hexafluoroisopropoxyborate prepared under argon atmosphere in Example 1;

[0034] Figure 4 The EIS-MS spectra of magnesium hexafluoroisopropoxyborate prepared under different atmospheres in Example 1;

[0035] Figure 5 The NMR spectra of magnesium hexafluoroisopropoxyborate obtained under argon atmosphere in Example 1 under different storage conditions are shown in Table 1. 1 H spectrum;

[0036] Figure 6 The NMR spectra of magnesium hexafluoroisopropoxyborate obtained under argon atmosphere in Example 1 under different storage conditions are shown in Table 1. 11 B spectrum;

[0037] Figure 7The NMR spectra of magnesium hexafluoroisopropoxyborate obtained under argon atmosphere in Example 1 under different storage conditions are shown in Table 1. 19 F spectrum;

[0038] Figure 8 The cycling performance of the boron-based magnesium salt obtained in Example 1 under an argon atmosphere at a current density of 1 mAh for a symmetrical battery of Mg|Mg[B(Ohfip)4]2 / DME|Mg;

[0039] Fig. 9 The coulombic efficiency of the Mg|Mg[B(Ohfip)4]2 / DME|Cu asymmetric battery of the boron-based magnesium salt obtained in Example 1 under argon atmosphere at a current density of 1 mAh. DETAILED DESCRIPTION

[0040] The present invention provides a method for efficiently and scalably preparing a high-stability boron-based magnesium salt, comprising the following steps:

[0041] Step 1: reacting a boron source and a magnesium source in an organic solvent to obtain a first reaction system;

[0042] Step 2: reacting the first reaction system with an alcohol source to obtain a second reaction system;

[0043] Step 3: Add a poor solvent to the second reaction system, wash the obtained precipitate, distill under reduced pressure and dry to obtain the boron-based magnesium salt.

[0044] In the present invention, unless otherwise specified, all preparation raw materials are commercially available products well known to those skilled in the art.

[0045] The present invention reacts a boron source with a magnesium source in an organic solvent to obtain a first reaction system.

[0046] In the present invention, the boron source preferably includes borane and / or a borane complex; the borane complex preferably includes one or more of dimethyl sulfide borane, borane triethylamine, borane tetrahydrofuran, borane ammonia complex, N,N-dimethylaniline borane and 1,2-diaryl-o-carborane; the purity of the boron source is preferably 95-99.9%.

[0047] In the present invention, the magnesium source preferably includes magnesium dihydride and / or an alkyl magnesium salt; the alkyl magnesium salt preferably includes one or more of diethyl magnesium, di-n-butyl magnesium, di-sec-butyl magnesium, dibutyl (isopropyl) magnesium, di-n-butyl ethyl magnesium and n-butyl sec-butyl magnesium.

[0048] In the present invention, the organic solvent preferably includes a non-polar solvent or an ether solvent, and more preferably a non-polar solvent; the non-polar solvent preferably includes one or more of toluene, hexane, petroleum ether, pentane, dimethylpentane, isooctane and heptane; the ether solvent preferably includes one or more of sulfide, tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether. In the present invention, the purity of the organic solvent is preferably>95%.

[0049] In the present invention, the molar ratio of the boron source to the organic solvent is preferably 1 mmol: 0.5-2.5 mL. In the present invention, the molar ratio of the magnesium source to the organic solvent is preferably 1 mmol: 1.0-6.0 mL. In the present invention, the molar ratio of the boron source to the magnesium source is preferably 1.5-4.0: 1.0.

[0050] In the present invention, the process of reacting the boron source and the magnesium source in an organic solvent is preferably: after dissolving the boron source in an organic solvent, adding the magnesium source to react.

[0051] In the present invention, the magnesium source is preferably added in the form of an organic solution containing the magnesium source; the solvent in the organic solution containing the magnesium source preferably includes a non-polar organic solvent and / or an ether organic solvent. The present invention has no particular limitation on the concentration of the organic solution containing the magnesium source, and any concentration known to those skilled in the art may be used.

[0052] In the present invention, the reaction temperature is preferably -5 to 110°C, the reaction time is preferably 5 to 180 min, and the pressure is preferably 0 to 15 MPa.

[0053] In the present invention, the reaction is preferably carried out under stirring, and the stirring speed is preferably 50 to 1500 rpm. In the present invention, the reaction is preferably carried out under atmospheric atmosphere or protective atmosphere; the ambient humidity of the atmospheric atmosphere is preferably <70%; the protective atmosphere is preferably an inert atmosphere, and more preferably argon.

[0054] In the present invention, after obtaining the first reaction system, it is preferred that the next step of reaction is directly carried out without any post-treatment process.

[0055] After obtaining the first reaction system, the present invention reacts the first reaction system with an alcohol source to obtain a second reaction system.

[0056] In the present invention, the alcohol source preferably includes monohydric alcohol compounds and / or polyhydric alcohol compounds; the monohydric alcohol compounds preferably include ethanol, difluoroethanol, trifluoroethanol, 1-phenyl-2,2,2-trifluoroethanol, isopropanol, 1,3-dibromo-2-propanol, 2-phenylisopropanol, trifluoropropanol, trifluoroisopropanol, hexafluoroisopropanol, perfluoro-tert-butyl alcohol, 2-trifluoromethyl-2-propanol, 3-perfluorobutyl propanol, 1,1,1,3,3,3-hexafluoro-2-phenylisopropanol, The polyol compound preferably includes one or more of ethylene glycol, 2,3-butanediol, 2,3-diphenyl-2,3-butanediol, 2,3-dimethyl-2,3-butanediol, 1,2,4-butanetriol and hexafluoro-2,3-bis(trifluoromethyl)-2,3-butanediol; the purity of the alcohol source is preferably 95 to 99.7%. In the present invention, the molar ratio of the magnesium source to the alcohol source is preferably 1.0:8.5 to 12.5.

[0057] In the present invention, the mixing order is preferably to add the alcohol source into the first reaction system. In the present invention, the reaction temperature is preferably -5 to 110°C, and the pressure is preferably 0 to 15 MPa; the second reaction is preferably carried out under stirring, and the stirring time is preferably 5 to 120 min.

[0058] In the present invention, after obtaining the second reaction system, it is preferred that the next step of reaction is directly carried out without any post-treatment process.

[0059] After obtaining the second reaction system, the present invention adds a poor solvent to the second reaction system, washes the obtained precipitate, distills it under reduced pressure and dries it to obtain the boron-based magnesium salt.

[0060] In the present invention, the poor solvent preferably includes one or more of toluene, n-hexane, cyclohexane, petroleum ether, n-pentane, isopentane, dimethylpentane, cyclopentane, isooctane and heptane; the purity of the poor solvent is preferably greater than 97%. In the present invention, the volume ratio of the second reaction system to the poor solvent is preferably 1:0.5-2.

[0061] The present invention has no special limitation on the washing process, and the process known to those skilled in the art can be adopted; the washing is preferably repeated 3 times.

[0062] In the present invention, the temperature of the reduced pressure distillation is preferably 30-60°C, and the time is preferably 5-180 min. In the present invention, the drying preferably includes vacuum drying and / or forced air drying; the temperature of the drying is preferably 50-90°C, and the time is preferably 2-24 h.

[0063] In the present invention, the yield of the boron-based magnesium salt is preferably 79-96%.

[0064] In the present invention, the reaction mechanism for preparing the boron-based magnesium salt is preferably:

[0065] 8BH3-R1+3Mg[R2]2→3Mg(BH4)2·2R1+2B(R2)3R1 Formula 1

[0066] Mg(BH4)2.2R1+9R3OH(excess)→Mg[B(OR3)4]2+8H2↑ Formula 2

[0067] The specific process of the present invention is preferably to use anion replacement method to make the boron source and the magnesium source react first to generate borohydride (Formula 1), and then directly react with the alcohol source to generate boro-based magnesium salt (Formula 2). The synthesis steps are simple, borohydride is generated in situ during the reaction, no other metal cations and chloride ions are introduced, and the cost is low.

[0068] The present invention also provides a high-stability boron-based magnesium salt prepared by the preparation method described in the above technical solution.

[0069] The present invention also provides the use of the high-stability boron-based magnesium salt described in the above technical solution in a magnesium battery electrolyte. The present invention has no special limitation on the specific implementation of the application, and those familiar to those skilled in the art can be used.

[0070] In order to further illustrate the present invention, a high-stability boron-based magnesium salt and its efficient and large-scale preparation method and application provided by the present invention are described in detail below in conjunction with the accompanying drawings and examples, but they should not be understood as limiting the scope of protection of the present invention.

[0071] Example 1

[0072] The raw materials were measured in the following amounts: 50 mmol of dimethyl sulfide borane; 98% of n-hexane organic solvent; di-n-butyl magnesium hexane solution (containing 20 mmol of di-n-butyl magnesium); and 175.0 mmol of 99.5% of hexafluoroisopropanol.

[0073] (1) In an atmosphere of air (ambient humidity <70%) or argon, dimethyl sulfide borane is first dissolved in 45 mL of n-hexane organic solvent, and then di-n-butyl magnesium hexane solution is added to the mixed solution and stirred for reaction at a stirring speed of 300 rpm, a reaction temperature of 20° C., a pressure of 0.2 MPa, and a reaction time of 60 min to obtain a first reaction system.

[0074] (2) Hexafluoroisopropanol was added to the first reaction system and stirred for reaction at a stirring speed of 300 rpm, a reaction temperature of 0° C., a pressure of 0.2 MPa, and a reaction time of 20 min to obtain a second reaction system.

[0075] (3) 80 mL of n-hexane was added to the second reaction system, and the obtained precipitate was washed repeatedly for 3 times; the supernatant was removed, and the mixture was distilled under reduced pressure at 40° C. for 20 min, and vacuum dried at 70° C. for 12 h to obtain 29.6 g of Mg[B(Ohfip)4]2 magnesium salt crystals with a yield of 90%.

[0076] Figure 1 is a SEM image of the intermediate product borohydride (i.e., the first reaction system) in the preparation process of argon atmosphere in Example 1; Figure 2 The XRD spectrum of the intermediate product borohydride in the preparation process of argon atmosphere in Example 1; Figure 3 This is a SEM image of magnesium hexafluoroisopropoxyborate obtained under argon atmosphere in Example 1. Figures 1-2 It can be seen that in the preparation process, the boron source and the magnesium source react to form borohydride first; at the same time, hexafluoroisopropoxy magnesium borate ( Figure 3 ).

[0077] Figure 4 : This is the EIS-MS spectrum of magnesium hexafluoroisopropoxyborate prepared under different atmospheres in Example 1; Figure 5 The NMR spectra of magnesium hexafluoroisopropoxyborate obtained under argon atmosphere in Example 1 under different storage conditions are shown in Table 1. 1 H spectrum; Figure 6 The NMR spectra of magnesium hexafluoroisopropoxyborate obtained under argon atmosphere in Example 1 under different storage conditions are shown in Table 1. 11 B spectrum; Figure 7 The NMR spectra of magnesium hexafluoroisopropoxyborate obtained under argon atmosphere in Example 1 under different storage conditions are shown in Table 1. 19 F spectrum; through Figures 4 to 7 ESI-MS negative spectrum and NMR 1 H. 11 B. 19 From the analysis of Figure F, it can be seen that the prepared magnesium borate salt has high purity, no by-products are generated, and good stability to air and water.

[0078] Example 2

[0079] The raw materials were measured according to the following amounts: 50 mmol of borane tetrahydrofuran; 99.5% of toluene organic solvent; n-hexane organic solvent with purity > 98%; di-n-butyl magnesium heptane solution (containing 20 mmol of di-n-butyl magnesium); and 175 mmol of 99.5% of hexafluoroisopropanol.

[0080] (1) Under an argon atmosphere, borane tetrahydrofuran was first dissolved in 50 mL of toluene organic solvent, and then di-n-butyl magnesium heptane solution was added to the mixed solution and stirred for reaction at a stirring speed of 300 rpm, a reaction temperature of 0° C., a pressure of 0.1 MPa, and a reaction time of 80 min to obtain a first reaction system.

[0081] (2) Hexafluoroisopropanol was added to the first reaction system and stirred for reaction at a stirring speed of 300 rpm, a reaction temperature of 0° C., a pressure of 0.1 MPa, and a reaction time of 30 min to obtain a second reaction system.

[0082] (3) 100 mL of n-hexane was added to the second reaction system, and the obtained precipitate was washed repeatedly for 3 times; the supernatant was removed, and the mixture was subjected to reduced pressure distillation at 40° C. for 20 min, and vacuum dried at 70° C. for 16 h, to obtain 31.0 g of Mg[B(Ohfip)4]2 magnesium salt crystals with a yield of 94%.

[0083] Example 3

[0084] The raw materials were measured according to the following amounts: 50 mmol of borane ammonia complex; 99.5% of tetrahydrofuran organic solvent; AR grade petroleum ether; di-n-butyl magnesium tetrahydrofuran solution (containing 20 mmol of di-n-butyl magnesium); and 180.0 mmol of 99.7% of ethanol.

[0085] (1) Under an argon atmosphere, firstly dissolve the borane ammonia complex in 50 mL of tetrahydrofuran organic solvent, then add the di-n-butyl magnesium tetrahydrofuran solution into the mixed solution and stir to react, the stirring speed is 300 rpm, the reaction temperature is 5° C., the pressure is 0.5 MPa, and the reaction time is 120 min to obtain a first reaction system.

[0086] (2) Add ethanol to the first reaction system and stir to react at a stirring speed of 300 rpm, a reaction temperature of 0° C., a pressure of 0.5 MPa, and a reaction time of 40 min to obtain a second reaction system.

[0087] (3) 100 mL of petroleum ether was added to the second reaction system, and the obtained precipitate was washed repeatedly for 3 times; the supernatant was removed, and vacuum distilled at 30° C. for 20 min, and vacuum dried at 45° C. for 12 h to obtain 30.2 g of Mg[B(Ohfip)4]2 magnesium salt crystals with a yield of 91%.

[0088] Example 4

[0089] The raw materials were measured according to the following amounts: 50 mmol of N,N-dimethylaniline borane; 99.5% of ethylene glycol dimethyl ether organic solvent; AR grade n-pentane; n-butyl sec-butyl magnesium heptane solution (containing 20 mmol of n-butyl sec-butyl magnesium); and 200.0 mmol of 99.5% of trifluoroethanol.

[0090] (1) Under an argon atmosphere, 50 mmol of N,N-dimethylaniline borane was first dissolved in 50 mL of ethylene glycol dimethyl ether organic solvent, and then n-butyl sec-butyl magnesium heptane solution was added to the mixed solution and stirred for reaction at a stirring speed of 300 rpm, a reaction temperature of 15° C., a pressure of 0.5 MPa, and a reaction time of 160 min to obtain a first reaction system.

[0091] (2) Add trifluoroethanol to the first reaction system and stir to react at a stirring speed of 300 rpm, a reaction temperature of 0° C., a pressure of 0.5 MPa, and a reaction time of 50 min to obtain a second reaction system.

[0092] (3) 100 mL of n-pentane was added to the second reaction system, and the obtained precipitate was washed repeatedly for 3 times; the supernatant was removed, and the mixture was subjected to reduced pressure distillation at 35° C. for 30 min, and vacuum dried at 50° C. for 12 h, to obtain 28.7 g of Mg[B(Otfe)4]2 magnesium salt crystals with a yield of 87%.

[0093] Example 5

[0094] The raw materials were measured according to the following amounts: 60 mmol of borane triethylamine; 80 mL of 99.5% triethylene glycol dimethyl ether organic solvent; isooctane with a purity of >99%; di-n-butyl ethyl magnesium hexane solution (containing 20 mmol of n-butyl sec-butyl magnesium); and 200.0 mmol of 99% perfluoro tert-butanol.

[0095] (1) Under an argon atmosphere, borane triethylamine was first dissolved in 80 mL of triethylene glycol dimethyl ether organic solvent, and then di-n-butyl ethyl magnesium hexane solution was added to the mixed solution and stirred for reaction at a stirring speed of 300 rpm, a reaction temperature of 10° C., a pressure of 0.5 MPa, and a reaction time of 180 min to obtain a first reaction system.

[0096] (2) Add perfluorotert-butyl alcohol to the first reaction system and stir to react at a stirring speed of 300 rpm, a reaction temperature of 0° C., a pressure of 0.5 MPa, and a reaction time of 60 min to obtain a second reaction system.

[0097] (3) 100 mL of isooctane was added to the second reaction system, and the obtained precipitate was washed repeatedly for 3 times; the supernatant was removed, and the mixture was subjected to reduced pressure distillation at 40°C for 20 min, and vacuum dried at 80°C for 24 h to obtain 26.8 g of Mg(BH(Opftb)3)2 magnesium salt crystals with a yield of 81%.

[0098] Example 6

[0099] The raw materials were measured according to the following amounts: 60 mmol of borane tetrahydrofuran; 98% of n-hexane organic solvent; n-hexane di-n-butyl magnesium heptane solution with a purity of >98% (containing 20 mmol of di-n-butyl magnesium); and 250 mmol of 98% of hexafluoro-2,3-bis(trifluoromethyl)-2,3-butanediol.

[0100] (1) Under an argon atmosphere, borane tetrahydrofuran was first dissolved in an organic solvent of n-hexane, and then a di-n-butyl magnesium heptane solution was added to the mixed solution and stirred for reaction at a stirring speed of 300 rpm, a reaction temperature of 25° C., a pressure of 0.2 MPa, and a reaction time of 20 min to obtain a first reaction system.

[0101] (2) Hexafluoro-2,3-bis(trifluoromethyl)-2,3-butanediol was added to the first reaction system and stirred for reaction at a stirring speed of 300 rpm, a reaction temperature of 60° C., a pressure of 0.2 MPa, and a reaction time of 120 min to obtain a second reaction system.

[0102] (3) 100 mL of n-hexane was added to the second reaction system, and the obtained precipitate was washed repeatedly for 3 times; the supernatant was removed, and the mixture was distilled under reduced pressure at 40° C. for 20 min, and vacuum dried at 70° C. for 10 h, and finally 29.8 g of MgFPB magnesium salt crystals were obtained, with a yield of 90%.

[0103] Application Examples

[0104] 1. Preparation of electrolyte system

[0105] Under the condition that the water oxygen content is less than 0.01 ppm, the hexafluoroisopropoxy magnesium salt obtained under argon atmosphere in Example 1 is added to ethylene glycol dimethyl ether (DME) solution to prepare an electrolyte with a magnesium salt concentration of 0.3 M (mol / L).

[0106] 2. Battery preparation and decomposition voltage test

[0107] Magnesium-magnesium symmetrical battery test method: Mg / Mg battery assembly test, assembled in the order of negative electrode shell, spring, gasket, magnesium sheet, GF / D glass fiber separator, magnesium sheet, positive electrode shell, add 60-100 microliters of electrolyte to each battery to wet the separator, and finally package the battery. The battery is first left for 5 minutes, then charged at 1mA / cm 2 The current density was used to test the cycling performance.

[0108] Magnesium-copper coulomb efficiency test method: Mg / Cu battery assembly test, assembled in the order of negative electrode shell, spring, gasket, magnesium sheet, GF / D glass fiber diaphragm, copper sheet, positive electrode shell, add 60-100 microliters of electrolyte to each battery to wet the diaphragm, and finally package the battery. The battery is first tested at 0.1 mA / cm in the voltage range of 0-1.5 V.2 The current density was used for pre-charge and discharge, and then the voltage was changed to 1.0 mA / cm 2 The deposition was carried out at a current density of 1.0 mA / cm 2 The stripping was carried out with a current density of 1.500 Å until the voltage was higher than 1.2 V, and the coulombic efficiency was calculated, where coulombic efficiency = discharge capacity / charge capacity.

[0109] Test results such as Figure 8 and Fig. 9 shown. Figure 8 The cycling performance of the boron-based magnesium salt obtained in Example 1 under an argon atmosphere at a current density of 1 mAh for a Mg|Mg[B(Ohfip)4]2 / DME|Mg symmetrical battery; Fig. 9 It is the coulombic efficiency of the Mg|Mg[B(Ohfip)4]2 / DME|Cu asymmetric battery of the boron-based magnesium salt obtained under argon atmosphere in Example 1 at a current density of 1 mAh.

[0110] from Figures 8-9 The test performance of symmetric and asymmetric batteries found that the electrolyte prepared by the prepared magnesium hexafluoroisopropoxyborate salt has good cycle performance (>300 cycles), low overpotential (0.15V) and high coulombic efficiency (94.34%).

[0111] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for efficiently and scalably preparing a high-stability boron-based magnesium salt, characterized in that: The following steps are involved: Step 1: reacting a boron source and a magnesium source in an organic solvent to obtain a first reaction system; the boron source comprises borane and / or a borane complex; the magnesium source comprises magnesium dihydride and / or an alkyl magnesium salt; Step 2: reacting the first reaction system with an alcohol source to obtain a second reaction system; the alcohol source includes a monohydric alcohol compound and / or a polyhydric alcohol compound; Step 3: adding a poor solvent to the second reaction system, washing the obtained precipitate, distilling under reduced pressure and drying to obtain the boron-based magnesium salt; The reaction temperature of step 1 is -5 to 110°C, the reaction time is 5 to 180 min, and the pressure is 0 to 15 MPa; the reaction is carried out under atmospheric atmosphere; The reaction temperature of step 2 is -5~110°C, the reaction time is 5~120min, and the pressure is 0~15MPa; The yield of the boron-based magnesium salt is 79-96%.

2. The method according to claim 1, characterized in that The organic solvent includes a non-polar solvent or an ether solvent; the non-polar solvent includes one or more of toluene, hexane, petroleum ether, pentane, dimethylpentane, isooctane and heptane; the ether solvent includes one or more of sulfide, tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether.

3. The method according to claim 1, characterized in that The borane complex comprises one or more of dimethyl sulfide borane, borane triethylamine, borane tetrahydrofuran, borane ammonia complex, N,N-dimethylaniline borane and 1,2-diaryl-o-carborane.

4. The method according to claim 1, characterized in that: The alkyl magnesium salt includes one or more of diethyl magnesium, di-n-butyl magnesium, di-sec-butyl magnesium, dibutyl (isopropyl) magnesium, di-n-butyl ethyl magnesium and n-butyl sec-butyl magnesium.

5. The method according to claim 1, characterized in that The monohydric alcohol compound includes one or more of ethanol, difluoroethanol, trifluoroethanol, 1-phenyl-2,2,2-trifluoroethanol, isopropanol, 1,3-dibromo-2-propanol, 2-phenylisopropanol, trifluoropropanol, trifluoroisopropanol, hexafluoroisopropanol, perfluoro-tert-butyl alcohol, 2-trifluoromethyl-2-propanol, 3-perfluorobutylpropanol, 1,1,1,3,3,3-hexafluoro-2-phenyl-2-propanol, 2,2-bis(trifluoromethyl)propanol, tetrahydropyran-4-ol and tetrahydrofuranmethanol; the polyhydric alcohol compound includes one or more of ethylene glycol, 2,3-butanediol, 2,3-diphenyl-2,3-butanediol, 2,3-dimethyl-2,3-butanediol, 1,2,4-butanetriol and hexafluoro-2,3-bis(trifluoromethyl)-2,3-butanediol.

6. The method according to claim 1, characterized in that The amount ratio of the boron source to the organic solvent is 1 mmol: 0.5-2.5 mL; The magnesium source and the organic solvent are used in a ratio of 1 mmol: 1.0-6.0 mL; The molar ratio of the boron source to the magnesium source is 1.5-4.0:1.0; The molar ratio of the magnesium source to the alcohol source is 1.0:8.5-12.

5.

7. The method according to claim 1, characterized in that The poor solvent includes one or more of toluene, n-hexane, cyclohexane, petroleum ether, n-pentane, isopentane, dimethylpentane, cyclopentane, isooctane and heptane; The volume ratio of the second reaction system to the poor solvent is 1:0.5-2; The temperature of the reduced pressure distillation is 30-60°C and the time is 5-180min; The drying includes vacuum drying and / or forced air drying; the drying temperature is 50-90° C. and the drying time is 2-24 hours.

8. The high-stability boron-based magnesium salt prepared by the method according to any one of claims 1 to 7.

9. Use of the high-stability boron-based magnesium salt according to claim 8 in magnesium battery electrolyte.

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