Preparation method of composite magnesium salt electrolyte of boron-based magnesium salt and alcohol / phenol magnesium additive

Abstract

The invention discloses a preparation method of a boron-based magnesium salt and alcohol / phenol magnesium additive composite magnesium salt electrolyte, and relates to the technical field of magnesium ion batteries, and the preparation method comprises the following steps: S1, in an inert atmosphere or an air environment, dissolving / dispersing a magnesium source in an organic solvent, and stirring to obtain a solution a; s2, adding alcohol or phenol into the solution a, and reacting to obtain a solution b; s3, performing post-treatment on the solution b to obtain alcohol magnesium salt or phenol magnesium salt crystals; and S4, co-dissolving alcohol magnesium salt or phenol magnesium salt and fluorine-containing alkoxy magnesium borate in an ether solvent according to a molar ratio of 1: (3-100) to form the composite magnesium salt electrolyte. According to the magnesium battery using the electrolyte, the cycle life can be prolonged by 20%-100%, the actual service cycle of the battery is prolonged, the coulombic efficiency is improved to 97%-99.5%, irreversible capacity loss in the charging and discharging process is reduced, the energy utilization efficiency is improved, the oxidation potential is improved by 0.2-0.5 V compared with that of a traditional electrolyte, the stability and oxidation resistance of the electrolyte are enhanced, and the service life of the magnesium battery is prolonged. And the working voltage window of the battery is widened.

Description

Technical Field

[0001] This invention relates to the field of magnesium-ion battery technology, specifically to a method for preparing a composite magnesium salt electrolyte of boron-based magnesium salt and alcohol / phenol magnesium additive. Background Technology

[0002] Magnesium-ion batteries are considered a strong candidate for next-generation large-scale energy storage technology due to their high theoretical volumetric capacity, abundant crustal reserves, low cost, and high safety caused by the non-dendritic formation of magnesium during deposition / dissolution. However, these batteries still face key challenges in practical applications due to insufficient electrolyte performance, mainly manifested in short cycle life, low coulombic efficiency, strong corrosivity, poor overall stability, and limited oxidation window.

[0003] In existing technologies, boron-based electrolytes, represented by magnesium fluoroalkoxyborate salts, have attracted attention due to their high ionic conductivity and good oxidation stability. However, the overall performance of these electrolytes still has certain limitations, such as short cycle life, low stability, and low coulombic efficiency. Studies have shown that introducing a small amount of functional additives can effectively regulate the interfacial properties of the electrolyte and improve its electrochemical performance. However, existing additive systems either have limited effects or are too expensive, making it difficult to balance performance and economic benefits. Therefore, developing high-performance, low-cost composite magnesium salt electrolytes based on novel additives has become crucial for promoting the development of magnesium batteries. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing a composite magnesium salt electrolyte of boron-based magnesium salt and alcohol / phenol magnesium additive, so as to solve the problems mentioned in the background art.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing a composite magnesium salt electrolyte of boron-based magnesium salt and alcohol / phenol magnesium additive, characterized by comprising the following steps:

[0007] S1: Dissolve / disperse the magnesium source in an organic solvent under an inert atmosphere or in air, and stir to obtain solution a;

[0008] S2: Add alcohol or phenol to solution a to react and obtain solution b;

[0009] S3: Post-process solution b by adding a non-polar solvent to precipitate the product, removing the supernatant, and obtaining magnesium alkoxide or magnesium phenolate crystals by vacuum distillation and vacuum drying.

[0010] S4: The magnesium alkoxide or magnesium phenolate and magnesium fluorinated alkoxyborate are dissolved together in an ether solvent at a molar ratio of 1:3 to 100 to form a composite magnesium salt electrolyte.

[0011] A further technical solution is that the magnesium source in step S1 is magnesium hydride or alkyl magnesium, wherein the alkyl magnesium includes, but is not limited to, di-n-butyl magnesium, di-n-butylethyl magnesium and n-butylsec-butyl magnesium, and the purity of the magnesium source is not less than 95%.

[0012] A further technical solution is that the organic solvent in step S1 is an inert organic solvent, which is an aliphatic hydrocarbon, aromatic hydrocarbon, ether or mixture thereof, including but not limited to one or more of toluene, hexane, petroleum ether, pentane, tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether, and the purity of the inert organic solvent is greater than 98%.

[0013] A further technical solution is that the ratio of the amount of magnesium source to the volume of organic solvent in step S1 is 1 mmol: 0.5-3.0 mL.

[0014] A further technical solution is that the alcohol in step S2 is a fatty alcohol or a halogenated fatty alcohol, and the purity of the alcohol is not less than 98%; the phenol is a phenolic substance, and the phenolic substance includes, but is not limited to, phenol, naphthol, cresol and their halogenated derivatives, and the purity of the phenol is not less than 98%.

[0015] A further technical solution is that the molar ratio of the magnesium source to the hydroxyl group in the alcohol or phenol in step S2 is 1.0:1.0~2.0.

[0016] A further technical solution is that in step S2, the reaction temperature is -40 to 50°C, the time is 10 minutes to 24 hours, and the stirring speed is 100 to 1000 rpm.

[0017] A further technical solution is that the non-polar solvent in step S3 is an aliphatic hydrocarbon, aromatic hydrocarbon, halogenated hydrocarbon, ether, or a mixture thereof. The non-polar solvent includes, but is not limited to, n-hexane, cyclohexane, petroleum ether, n-pentane, toluene, mesitylene, dichloromethane, and diethyl ether, with a purity >97%.

[0018] A further technical solution is that the vacuum distillation temperature in step S3 is 20-80℃; and the vacuum drying temperature is 40-80℃.

[0019] Reaction mechanism:

[0020] The magnesium source reacts with alcohols or phenols to displace hydrogen or alkanes, generating corresponding magnesium alcohols or magnesium phenols additives, for example:

[0021] Mg(R1)2+2R2OH→Mg(OR2)2+2R1H↑

[0022] R1 is hydrogen or alkyl, and R2 is a haloalkyl or haloaromatic group. The resulting magnesium alkoxide or magnesium phenolate can be applied to boron-based magnesium salt electrolytes to regulate their solvation structure, while also exhibiting excellent interfacial modification capabilities, effectively stabilizing the electrolyte and improving battery performance.

[0023] Due to the adoption of the above technical solution, the technical progress achieved by this invention compared to the prior art is as follows:

[0024] 1. This invention provides a method for preparing a composite magnesium salt electrolyte of boron-based magnesium salt and alcohol / phenol magnesium additive. After using this electrolyte, the cycle life of magnesium batteries can be increased by 20%-100%, extending the actual service life of the battery. The coulombic efficiency is increased to 97%-99.5%, reducing irreversible capacity loss during charging and discharging, improving energy utilization efficiency, and increasing the oxidation potential by 0.2-0.5V compared with traditional electrolytes, enhancing the stability and oxidation resistance of the electrolyte, and widening the working voltage window of the battery.

[0025] 2. This invention provides a method for preparing a composite magnesium salt electrolyte of boron-based magnesium salt and alcohol / phenol magnesium additive, which improves the magnesium deposition morphology, forms a more uniform and dense metallic magnesium coating, inhibits dendrite growth and the generation of "dead magnesium", and effectively suppresses the side reactions between the electrolyte and electrode materials, reduces the interfacial impedance, and further improves the safety of the battery.

[0026] 3. This invention provides a method for preparing a composite magnesium salt electrolyte of boron-based magnesium salt and alcohol / phenol magnesium additive. In practical applications, the concentration of magnesium salt, the ratio of alcohol magnesium additive, and the type and ratio of solvent can be flexibly adjusted according to the requirements of battery operating temperature, rate performance and cycle life, so as to achieve precise control of electrolyte performance. Attached Figure Description

[0027] Figure 1 The mass spectrum of the magnesium pentafluorophenol prepared in Example 1 of this invention;

[0028] Figure 2 The image shows the cycle performance of the electrolyte symmetric battery prepared in Example 1 of this invention.

[0029] Figure 3 The cyclic voltammetry diagram of the electrolyte asymmetric battery prepared in Example 1 of this invention;

[0030] Figure 4 This is a charge-discharge curve of the electrolyte full battery prepared in Example 1 of the present invention;

[0031] Figure 5 This is a deposition morphology image of the electrolyte symmetric battery prepared in Example 1 of the present invention after cycling; Detailed Implementation

[0032] The present invention will be further described in detail below with reference to embodiments:

[0033] The present invention has the following four specific embodiments.

[0034] Example 1

[0035] Raw material ratio: di-n-butylmagnesium 20 mmol; 99.5% ethylene glycol dimethyl ether 20 mL; pentafluorophenol 40 mmol; magnesium hexafluoroisopropoxide borate; ethylene glycol dimethyl ether solvent.

[0036] Preparation steps:

[0037] (1) In an inert atmosphere reactor, 20 mmol of di-n-butylmagnesium was dissolved in 20 mL of ethylene glycol dimethyl ether and stirred until homogeneous to obtain solution a;

[0038] (2) Add 40 mmol of pentafluorophenol to solution a, control the reaction temperature at 25℃ and the stirring speed at 500 rpm, and react for 30 minutes to obtain solution b;

[0039] (3) Add 60 mL of n-hexane with a purity >98% to solution b, wash the precipitate twice, and remove the supernatant;

[0040] (4) The sample was distilled under reduced pressure at 50°C and then dried under vacuum at 60°C for 6 hours to obtain pentafluorophenoxy magnesium salt crystals with a yield of 92%.

[0041] (5) A composite magnesium salt electrolyte was prepared by dissolving magnesium pentafluorophenoxy and magnesium hexafluoroisopropoxide borate in ethylene glycol dimethyl ether at a molar ratio of 1:10.

[0042] Performance testing:

[0043] Mass spectrometry analysis ( Figure 1 The product was confirmed to be the target pentafluorophenoxy magnesium salt, with no byproducts generated.

[0044] Symmetrical cell test ( Figure 2 The results show that the electrolyte exhibits excellent cycling stability at a current density of 1 mAh.

[0045] Asymmetric battery testing ( Figure 3 The results show that the electrolyte has excellent reversible deposition dissolution capabilities.

[0046] Full battery test ( Figure 4 The results show that the Mg||CuS full cell has an 80% improvement in cycle life and a 50% improvement in capacity at a current density of 100 mA・g⁻¹.

[0047] Sedimentary morphology ( Figure 5 The magnesium deposition is uniform and dense, with no obvious dendrite formation.

[0048] Example 2

[0049] Raw material ratio: di-n-butylethyl magnesium (heptane solution) 20 mmol; 99.5% ethylene glycol dimethyl ether 40 mL; perfluorotert-butanol 45 mmol; perfluoropinacol magnesium borate; diethylene glycol dimethyl ether solvent.

[0050] Preparation steps:

[0051] (1) In an inert atmosphere reactor, 20 mmol of di-n-butylethyl magnesium was dissolved in 40 mL of ethylene glycol dimethyl ether and stirred to obtain solution a;

[0052] (2) Add 45 mmol of perfluorotert-butanol to solution a, control the reaction temperature at 30℃ and the stirring speed at 400 rpm, and react for two hours to obtain solution b;

[0053] (3) Add 80 mL of n-hexane to solution b, wash the precipitate 3 times, and remove the supernatant;

[0054] (4) The magnesium perfluorotert-butoxy salt crystals were obtained by vacuum distillation at 45°C and vacuum drying at 50°C for 8 hours.

[0055] (5) The magnesium salt perfluorotert-butoxy and magnesium perfluoropinacolborate were dissolved together in diethylene glycol dimethyl ether at a molar ratio of 1:5 to prepare a composite magnesium salt electrolyte.

[0056] Example 3

[0057] Raw material ratio: 20 mmol of n-butyl-sec-butyl magnesium; 50 mL of 99.5% diethylene glycol dimethyl ether; 45 mmol of pentabromophenol; magnesium trifluoroethanolborate; a 1:1 mixture of tetraethylene glycol dimethyl ether and tetrahydrofuran solvent.

[0058] Preparation steps:

[0059] (1) In an inert atmosphere reactor, 20 mmol of n-butyl-sec-butyl magnesium was dissolved in 50 mL of diethylene glycol dimethyl ether and stirred to obtain solution a;

[0060] (2) Add 45 mmol of pentabromophenol to solution a, control the reaction temperature at 10℃ and the stirring speed at 600 rpm, and react for 4 hours to obtain solution b;

[0061] (3) Add 60 mL of n-hexane with a purity >97% to solution b, wash the precipitate twice, and remove the supernatant;

[0062] (4) Distilled under reduced pressure at 40°C and dried under vacuum at 50°C for 10 hours to obtain pentabromophenoxy magnesium salt crystals;

[0063] (5) A composite magnesium salt electrolyte was prepared by dissolving magnesium pentabromophenoxy salt and magnesium trifluoroethanolborate in a 1:20 molar ratio in a 1:1 mixed solvent of tetraethylene glycol dimethyl ether and tetrahydrofuran.

[0064] Example 4

[0065] Raw material ratio: 20 mmol magnesium dihydrogen ether; 40 mL 99.5% triethylene glycol dimethyl ether; 50 mmol trifluoroethanol; magnesium hexafluoroisopropoxide borate; triethylene glycol dimethyl ether.

[0066] Preparation steps:

[0067] (1) In an inert atmosphere reactor, 20 mmol of magnesium dihydrogen ether was dispersed in 40 mL of triethylene glycol dimethyl ether and stirred to obtain solution a;

[0068] (2) Add 50 mmol of trifluoroethanol to solution a, control the reaction temperature at -40℃ and the stirring speed at 300 rpm, and react for 10 hours to obtain solution b;

[0069] (3) Add 120 mL of n-hexane to solution b, wash the precipitate 3 times, and remove the supernatant;

[0070] (4) Distilled under reduced pressure at 55°C and dried under vacuum at 65°C for 7 hours to obtain magnesium trifluoroethoxy salt crystals;

[0071] (5) The magnesium trifluoroethoxy salt and magnesium hexafluoroisopropoxide borate were dissolved together in triethylene glycol dimethyl ether at a molar ratio of 1:50 to prepare a composite magnesium salt electrolyte.

[0072] The present invention has been described in detail above. However, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, any modifications or improvements that do not depart from the spirit of the present invention are within the scope of protection of the present invention.

Claims

1. A method for preparing a composite magnesium salt electrolyte of boron-based magnesium salt and alcohol / phenol magnesium additive, characterized in that: Includes the following steps: S1: Dissolve / disperse the magnesium source in an organic solvent under an inert atmosphere or in air, and stir to obtain solution a; S2: Add alcohol or phenol to solution a to react and obtain solution b; S3: Post-process solution b by adding a non-polar solvent to precipitate the product, removing the supernatant, and obtaining magnesium alkoxide or magnesium phenolate crystals by vacuum distillation and vacuum drying. S4: The magnesium alkoxide or magnesium phenolate and magnesium fluorinated alkoxyborate are dissolved together in an ether solvent at a molar ratio of 1:3 to 100 to form a composite magnesium salt electrolyte.

2. The method for preparing a composite magnesium salt electrolyte of boron-based magnesium salt and alcohol / phenol magnesium additive according to claim 1, characterized in that: The magnesium source in step S1 is magnesium hydride or alkyl magnesium, and the alkyl magnesium includes, but is not limited to, di-n-butyl magnesium, di-n-butylethyl magnesium and n-butylsec-butyl magnesium, and the purity of the magnesium source is not less than 95%.

3. The method for preparing a composite magnesium salt electrolyte of boron-based magnesium salt and alcohol / phenol magnesium additive according to claim 1, characterized in that: The organic solvent in step S1 is an inert organic solvent, which is an aliphatic hydrocarbon, aromatic hydrocarbon, ether or mixture thereof, including but not limited to one or more of toluene, hexane, petroleum ether, pentane, tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether, and the purity of the inert organic solvent is greater than 98%.

4. The method for preparing a composite magnesium salt electrolyte of boron-based magnesium salt and alcohol / phenol magnesium additive according to claim 1, characterized in that: In step S1, the ratio of the amount of magnesium source to the volume of organic solvent is 1 mmol: 0.5–3.0 mL.

5. The method for preparing a composite magnesium salt electrolyte of boron-based magnesium salt and alcohol / phenol magnesium additive according to claim 1, characterized in that: In step S2, the alcohol is a fatty alcohol or a halogenated fatty alcohol, and the purity of the alcohol is not less than 98%; the phenol is a phenolic substance, and phenolic substances include, but are not limited to, phenol, naphthol, cresol and their halogenated derivatives, and the purity of the phenol is not less than 98%.

6. The method for preparing a composite magnesium salt electrolyte of boron-based magnesium salt and alcohol / phenol magnesium additive according to claim 1, characterized in that: In step S2, the molar ratio of the magnesium source to the hydroxyl group in the alcohol or phenol is 1.0:1.0 to 2.

0.

7. The method for preparing a composite magnesium salt electrolyte of boron-based magnesium salt and alcohol / phenol magnesium additive according to claim 1, characterized in that: In step S2, the reaction temperature is -40 to 50°C, the time is 10 minutes to 24 hours, and the stirring speed is 100 to 1000 rpm.

8. The method for preparing a composite magnesium salt electrolyte of boron-based magnesium salt and alcohol / phenol magnesium additive according to claim 1, characterized in that: In step S3, the nonpolar solvent is an aliphatic hydrocarbon, aromatic hydrocarbon, halogenated hydrocarbon, ether, or a mixture thereof. The nonpolar solvent includes, but is not limited to, n-hexane, cyclohexane, petroleum ether, n-pentane, toluene, mesitylene, dichloromethane, and diethyl ether, with a purity >97%.

9. The method for preparing a composite magnesium salt electrolyte of boron-based magnesium salt and alcohol / phenol magnesium additive according to claim 1, characterized in that: In step S3, the reduced pressure distillation temperature is 20–80°C; the vacuum drying temperature is 40–80°C.

10. The method for preparing a composite magnesium salt electrolyte of boron-based magnesium salt and alcohol / phenol magnesium additive according to claim 1, characterized in that: The molar ratio of the magnesium alkoxide or magnesium phenolate to the magnesium fluorinated alkoxyborate is 1:3 to 100; the magnesium fluorinated alkoxyborate includes, but is not limited to, magnesium trifluoroethanolborate, magnesium perfluoropinacolborate, and magnesium hexafluoroisopropoxideborate; the ether solvents include, but are not limited to, one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and tetrahydrofuran.

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