Electrolyte and preparation method thereof, battery monomer, secondary battery and electric device

Abstract

The invention discloses an electrolyte and a preparation method thereof, a battery monomer, a secondary battery and an electric device, and belongs to the technical field of magnesium ion secondary batteries. The electrolyte comprises magnesium-containing boride and alkali metal salt, the magnesium-containing boride has a B-O bond, and a B element in the magnesium-containing boride exists in the electrolyte in a tetra-coordinated form; according to the present invention, the magnesium-containing boride having the B-O bond and the B element existing in the electrolyte in the tetra-coordinated form is matched with the alkali metal salt to form the component of the electrolyte, such that the SEI film using the alkali metal boride having the B-O bond and containing the Mg element as the component can be formed in situ on the surface of the negative electrode plate in the battery, the alkali metal boride can effectively enhance the stability of the SEI membrane, so that the battery has lower overpotential, longer cycle life and higher specific capacity.

Description

Technical Field

[0001] This application relates to the field of magnesium-ion secondary battery technology, specifically to electrolytes and their preparation methods, battery cells, secondary batteries, and electrical devices. Background Technology

[0002] As energy storage technology advances towards higher energy densities, research focus has gradually shifted beyond the current mainstream lithium-ion batteries. Utilizing multivalent ions to replace monovalent lithium ions is considered one of the effective ways to achieve high-energy-density commercial rechargeable batteries. Magnesium (Mg) metal is favored due to its abundant reserves (8th highest among crustal elements), low reduction potential (-2.356 V vs. SHE), resistance to dendrite formation, and high volumetric energy density (3833 mAh / cm³). 3 With its advantages such as [missing information], it is considered one of the most promising new energy storage systems.

[0003] However, a key challenge in constructing high-performance magnesium-ion batteries lies in the continuous optimization of the solid electrolyte interphase (SEI) film on the magnesium anode surface. While existing mainstream magnesium salt systems each possess unique characteristics, exhibiting acceptable overpotentials and capable of forming SEI films in magnesium-magnesium symmetric batteries, their composition and stability still have significant room for optimization, making it difficult to fully meet the stringent requirements of high-performance full batteries for low polarization, high specific capacity, and long cycle life. Therefore, providing an electrolyte that can be universally applied to various magnesium salt systems, enhancing SEI film stability through the construction of specific components, and thereby simultaneously improving the specific capacity and cycle life of the magnesium-ion battery system, remains a significant technological gap and an urgent need. Summary of the Invention

[0004] In view of the above problems, this application provides an electrolyte that can be universally applied to a variety of magnesium salt systems, can construct a highly stable SEI film, and thus enable batteries using this electrolyte to have lower overpotential, better cycle life and higher specific capacity.

[0005] In a first aspect, this application provides an electrolyte, which is a magnesium-ion battery electrolyte. The electrolyte includes magnesium boride and alkali metal salt. The magnesium boride has BO bonds, and the B element in the magnesium boride exists in the electrolyte in a tetracoordinate form.

[0006] In the technical solution of this application embodiment, by using magnesium boride containing BO bonds and alkali metal salts in the electrolyte in a four-coordinate form as components of the electrolyte, an SEI film containing Mg and BO bonds as components can be formed in situ on the surface of the negative electrode in the battery. The alkali metal boride can effectively enhance the stability of the SEI film, so that the battery has a lower overpotential, better cycle life and higher specific capacity.

[0007] As an optional implementation, the molar ratio of magnesium boride to alkali metal salt is 1:0.05~1.

[0008] In the above implementation process, by controlling the molar ratio of magnesium boride and alkali metal salt to 1:0.05~1, the stability of the SEI film can be enhanced, resulting in a battery with lower overpotential, better cycle life and higher specific capacity.

[0009] As an optional implementation, the molar concentration of the magnesium boride in the electrolyte is 0.1 mol / L to 0.8 mol / L; and / or The mass concentration of alkali metal salts in the electrolyte is 0.01 mol / L to 0.5 mol / L.

[0010] As an alternative implementation, the magnesium boride is a magnesium borate ester.

[0011] As an alternative implementation, the alkali metal salt includes at least one of lithium, sodium, or potassium salts.

[0012] As an optional implementation, the magnesium borate ester includes Mg[B(OR1)4]2 or Mg[B(OR2)]2. n (NR3) 4-n At least one of 2, wherein R1, R2 and R3 independently include at least one of ethyl, 2,2-difluoroethyl, 2,2,2-trifluoroethyl, 1-phenyl-2,2,2-trifluoroethyl, isopropyl, 1,3-dibromo-2-propyl, 1-phenylethyl, 3,3,3-trifluoropropyl, 1,1,1-trifluoro-2-propyl, hexafluoroisopropyl, perfluorotert-butyl, 2-trifluoromethyl-2-propyl, 3-perfluorobutylpropyl, 1,1,1,3,3,3-hexafluoro-2-phenyl-2-propyl, 2,2-bis(trifluoromethyl)propyl or tetrahydrofuranmethyl.

[0013] As an alternative implementation, the lithium salt includes at least one of lithium chloride, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium nitrate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl)imide, or lithium hydroxide.

[0014] As an alternative implementation, the sodium salt includes at least one of sodium bis(fluorosulfonyl)imide, sodium hexafluorophosphate, sodium trifluoromethanesulfonate, or sodium bis(trifluoromethanesulfonyl)imide.

[0015] As an alternative implementation, the potassium salt includes at least one of potassium bis(fluorosulfonyl)imide, potassium hexafluorophosphate, potassium trifluoromethanesulfonate, or potassium bis(trifluoromethanesulfonyl)imide.

[0016] As an alternative implementation, magnesium borate esters are prepared by reacting borate esters with magnesium salts.

[0017] As an optional implementation, the borate ester includes at least one of trimethyl borate, triethyl borate, triisopropyl borate, tri-n-butyl borate, tris(2,2,2-trifluoroethyl) borate, hexafluoroborate, tris(pentafluorophenyl)borane, pinacol borane, pinacol borate, catechol borane, catechol borate, 1,8-naphthyldiaminoborate, MIDA borate, diethanolamine borate, bis(neopentylethylene glycol) diborate, bis(pinacol) diborate, bis(catechol) diborate, or pinacol diborate.

[0018] As an alternative implementation, the magnesium salt is prepared by reacting a magnesium source with a nucleophile.

[0019] As an alternative implementation, the magnesium source includes at least one of magnesium dihydrogenate, alkyl magnesium salt, or carboxylated magnesium salt.

[0020] As an optional implementation, the alkyl magnesium salt includes at least one of diethyl magnesium, di-n-butyl magnesium, di-sec-butyl magnesium, di-butyl (isopropyl) magnesium, di-n-butylethyl magnesium, or n-butyl-sec-butyl magnesium.

[0021] As an alternative implementation, the carboxylated magnesium salt includes at least one of magnesium formate, magnesium acetate, magnesium propionate, and / or magnesium formate.

[0022] As an optional implementation, the nucleophile includes at least one of an alcohol, an acid, or an amine.

[0023] As an optional implementation, the alcohol compound includes at least one of a monohydric alcohol compound or a polyhydric alcohol compound.

[0024] As an optional implementation, the monohydric alcohol compound includes at least one of ethanol, difluoroethanol, trifluoroethanol, 1-phenyl-2,2,2-trifluoroethanol, isopropanol, 1,3-dibromo-2-propanol, 2-phenylisopropanol, trifluoropropanol, trifluoroisopropanol, hexafluoroisopropanol, perfluorotert-butanol, 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, or tetrahydrofuran-methanol.

[0025] As an alternative implementation, the polyol compound includes at least one of ethylene glycol, 2,3-butanediol, 2,3-diphenyl-2,3-butanediol, 2,3-dimethyl-2,3-butanediol, 1,2,4-butanetriol or hexafluoro-2,3-bis(trifluoromethyl)-2,3-butanediol.

[0026] As an optional implementation, the acid compound includes at least one of a monobasic acid compound or a polybasic acid compound.

[0027] As an optional implementation, the monocarboxylic acid compound includes at least one of formic acid, acetic acid, propionic acid, 2,2-dimethylpropionic acid, benzoic acid, phenylacetic acid, 2-hydroxy-2-phenylacetic acid, trifluoroacetic acid, valeric acid, hexanoic acid, octanoic acid, p-toluenesulfonic acid, p-methoxybenzoic acid, trifluoromethanesulfonic acid, fluorosulfonic acid, hydrochloric acid, or hexafluorophosphate.

[0028] As an optional implementation, the polybasic acid compound includes at least one selected from oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, maleic acid, trans-butenedioic acid, phthalic acid, isophthalic acid, terephthalic acid, 2,3-dihydroxysuccinic acid, 2-hydroxysuccinic acid, 2-hydroxypropane-1,2,3-tricarboxylic acid, isocitric acid, propene-1,2,3-tricarboxylic acid, trimesic acid, trimesic acid, ethylenediaminetetraacetic acid, inositol hexaphosphate, sulfuric acid, phosphoric acid, carbonic acid, sulfurous acid, boric acid, or silicic acid.

[0029] As an optional implementation, the amine compound preferably includes at least one of hexamethyldisilazane, hexaethyldisilazane, tris(trimethylsilyl)amine, N,N-bis(trimethylsilyl)methylamine, bis(trifluoromethanesulfonyl)imide, bis(fluorosulfonyl)imide, bis(pentafluoroethanesulfonyl)imide or bis(dimethylamino)tert-butylamine.

[0030] As an optional implementation, the electrolyte also includes a solvent, which includes at least one of ether solvents or amine solvents.

[0031] As an optional implementation, at least one of the following is used: ether solvent, chain ether solvent, or cyclic ether solvent.

[0032] As an optional implementation, the chain ether solvent includes at least one of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, or tetraethylene glycol dimethyl ether.

[0033] As an alternative implementation, the cyclic ether solvent includes at least one of tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, or 1,3-dioxolane.

[0034] As an optional implementation, the amine solvent includes at least one of chain alkoxyamine solvents or cyclic alkoxyamine solvents.

[0035] As an optional implementation, the chain alkoxyamine solvent includes at least one of 2-methoxyethylamine, 2-ethoxyethylamine, 3-methoxypropylamine, 1-methoxy-2-propylamine, 2-(2-methoxyethoxy)ethylamine, N-(2-methoxyethyl)ethylamine or 2-(dimethylamino)ethyl methyl ether.

[0036] As an optional implementation, the cyclic alkoxyamine solvent includes at least one of 2-(2-methoxyethyl)morpholine, 4-methoxymethylpiperidine, N-(2-methoxyethyl)tetrahydropyrrole, 3-methoxyazacyclobutane or 2-(methoxymethyl)tetrahydrofuran-3-amine.

[0037] Secondly, embodiments of this application provide a method for preparing an electrolyte, the method comprising: The magnesium salt and the boride with BO bond are reacted first to obtain the magnesium boride; A magnesium boride and an alkali metal salt are mixed to obtain an electrolyte, which is a magnesium-ion battery electrolyte. The boron element in the magnesium boride exists in the electrolyte in a tetracoordinate form.

[0038] In the technical solution of this application embodiment, an electrolyte is formed by combining magnesium boride containing BO bonds and alkali metal salts in the electrolyte in a four-coordinated form. In the battery, an SEI film containing Mg and BO bonds as components can be formed in situ on the surface of the negative electrode. The alkali metal boride can effectively enhance the stability of the SEI film, so that the battery has a lower overpotential, better cycle life and higher specific capacity.

[0039] As an optional implementation method, the preparation method of magnesium salt includes: subjecting a magnesium source and a nucleophile to a second reaction to obtain a magnesium salt.

[0040] Thirdly, embodiments of this application provide a battery cell, which is a magnesium-ion battery, and the battery cell includes the electrolyte provided in the first aspect or the electrolyte prepared by the method provided in the second aspect.

[0041] As an optional implementation, the battery cell includes a negative electrode sheet, at least a portion of the surface of which is covered with an SEI film. The SEI film is composed of alkali metal borides, which contain Mg and have BO bonds.

[0042] As an alternative implementation, alkali metal borides include Mg[B(OR4)4]2[M + ] or Mg[B(OR5) n (NR6) 4-n ]2[M +At least one of the following, wherein R4, R5 and R6 independently include at least one of ethyl, 2,2-difluoroethyl, 2,2,2-trifluoroethyl, 1-phenyl-2,2,2-trifluoroethyl, isopropyl, 1,3-dibromo-2-propyl, 1-phenylethyl, 3,3,3-trifluoropropyl, 1,1,1-trifluoro-2-propyl, hexafluoroisopropyl, perfluorotert-butyl, 2-trifluoromethyl-2-propyl, 3-perfluorobutylpropyl, 1,1,1,3,3,3-hexafluoro-2-phenyl-2-propyl, 2,2-bis(trifluoromethyl)propyl or tetrahydrofuranmethyl, and M includes an alkali metal element.

[0043] As an optional implementation, the battery cell is a magnesium oxide battery, a magnesium sulfide battery, a magnesium sulfide battery, or a magnesium organic battery.

[0044] Fourthly, this application provides a secondary battery, which includes the battery cell provided in the third aspect.

[0045] Fifthly, this application provides an electrical device, which includes a battery cell provided in the third aspect or a secondary battery provided in the fourth aspect. Attached Figure Description

[0046] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 This is a flowchart illustrating the methods provided in some embodiments of this application.

[0047] Figure 2 XPS elemental analysis of the SEI film on the surface of the magnesium metal anode after the electrolyte prepared in Example 1 is cycled in a magnesium symmetric battery.

[0048] Figure 3 XPS elemental analysis of the SEI film on the surface of the magnesium metal anode after the electrolyte prepared in Example 2 is cycled in a magnesium symmetric battery.

[0049] Figure 4 XPS elemental analysis of the SEI film on the surface of the magnesium metal anode after the electrolyte prepared in Example 3 was cycled in a magnesium symmetric battery.

[0050] Figure 5 The image shows the liquid NMR results of the electrolyte prepared in Example 3.

[0051] Figure 6 This is a SEM image of the magnesium metal anode surface after the electrolyte prepared in Example 3 has been cycled in a magnesium symmetric battery.

[0052] Figure 7 The electrolytes provided for Example 1 (left) and Comparative Example 1 (right) were at 1 mA / cm 2 Cycle performance of magnesium-magnesium symmetric cells at current density.

[0053] Figure 8 The electrolytes provided for Example 2 (left) and Comparative Example 2 (right) were at 1 mA / cm 2 Cycle performance of magnesium-magnesium symmetric cells at current density.

[0054] Figure 9 The electrolytes provided for Example 3 (left) and Comparative Example 3 (right) were at 1 mA / cm 2 Cycle performance of magnesium-magnesium symmetric cells at current density.

[0055] Figure 10 The electrolyte provided for Comparative Example 5 was at 1 mA / cm 2 Cycle performance of magnesium-magnesium symmetric cells at current density.

[0056] Figure 11 The specific capacity-voltage performance of the magnesium oxide battery with the electrolyte provided in Comparative Example 3 at a current density of 50 mA / g.

[0057] Figure 12 The specific capacity-voltage performance of the magnesium oxide battery with the electrolyte provided in Example 3 at a current density of 50 mA / g.

[0058] Figure 13 The specific capacity-voltage performance of the magnesium oxide battery with the electrolyte provided in Comparative Example 5 at a current density of 50 mA / g.

[0059] Figure 14 The specific capacity-voltage performance of the magnesium sulfide battery provided in Comparative Example 3 at a current density of 200 mA / g.

[0060] Figure 15 The specific capacity-voltage performance of the magnesium sulfide battery provided in Example 3 at a current density of 200 mA / g is shown.

[0061] Figure 16 The specific capacity-voltage performance of the magnesium sulfide battery provided in Comparative Example 5 at a current density of 200 mA / g.

[0062] Figure 17 The specific capacity-voltage performance of the magnesium-sulfur battery provided in Comparative Example 3 at a current density of 167.5 mA / g.

[0063] Figure 18The specific capacity-voltage performance of the magnesium-sulfur battery provided in Example 3 at a current density of 167.5 mA / g is shown.

[0064] Figure 19 The specific capacity-voltage performance of the magnesium-sulfur battery provided in Comparative Example 5 at a current density of 167.5 mA / g. Detailed Implementation

[0065] The present application is hereby disclosed in detail with appropriate reference to the accompanying drawings. However, some unnecessary details may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of essentially the same structures may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter of the claims.

[0066] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for a specific parameter, it is also expected that ranges of 60~110 and 80~120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this application, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0067] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0068] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0069] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, if a method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if a method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc. In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined. In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0070] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0071] Magnesium (Mg) metal is considered one of the most promising new energy storage systems due to its abundant reserves (ranked 8th among crustal elements), low reduction potential (-2.356 V vs. SHE), resistance to dendrite formation, and high volumetric energy density (3833 mAh / cm³).

[0072] However, a key challenge in constructing high-performance magnesium-ion batteries lies in the continuous optimization of the solid electrolyte interphase (SEI) film on the magnesium anode surface. While existing mainstream magnesium salt systems each possess unique characteristics, exhibiting acceptable overpotentials and capable of forming SEI films in magnesium-magnesium symmetric batteries, their composition and stability still have significant room for optimization, making it difficult to fully meet the stringent requirements of high-performance full batteries for low polarization, high specific capacity, and long cycle life. Therefore, providing an electrolyte that can be universally applied to various magnesium salt systems, enhancing SEI film stability through the construction of specific components, and thereby simultaneously improving the specific capacity and cycle life of the magnesium-ion battery system, remains a significant technological gap and an urgent need.

[0073] In view of the above problems, this application provides an electrolyte that can be universally applied to a variety of magnesium salt systems, can construct a highly stable SEI film, and thus enable batteries using this electrolyte to have lower overpotential, better cycle life and higher specific capacity.

[0074] Electrolyte This application provides an electrolyte, which is a magnesium-ion battery electrolyte. The electrolyte includes magnesium boride and alkali metal salt. The magnesium boride has BO bonds, and the B element in the magnesium boride exists in the electrolyte in a tetracoordinate form.

[0075] The determination of electrolyte components (e.g., magnesium borides and alkali metal salts) can be performed as follows: In a nitrogen-filled glove box, add 500 μl of deuterated reagent to an NMR tube, then add 100 μl of the non-aqueous electrolyte sample to the NMR tube. Shake the NMR tube to dissolve the non-aqueous electrolyte in the deuterated reagent. Perform the analysis using an Oxford Instruments X-Pulse benchtop NMR spectrometer. Because the non-aqueous electrolyte is highly sensitive to moisture, both the NMR analysis and sample preparation are conducted in a nitrogen atmosphere (H₂O content less than 0.1 ppm, O₂ content less than 0.1 ppm). Simultaneously, all instruments used in the analysis must be pre-washed with pure water and dried in a vacuum environment at 60°C for at least 48 hours. The deuterated reagent was prepared as follows: Deuterated dimethyl sulfoxide (DMSO-d6), deuterated acetonitrile, and trifluoromethylbenzene were dried using a 4A molecular sieve at a temperature above 25°C for at least 3 days, ensuring that the water content of all reagents was less than 3 ppm. A Metrohm 831 KF coulometric moisture analyzer was used for moisture testing. Then, in a nitrogen-filled glove box, 10 ml of dried DMSO-d6 and 300 μl of dried internal standard trifluoromethylbenzene were mixed thoroughly to obtain the first solution. 10 ml of dried deuterated acetonitrile and 300 μl of dried internal standard trifluoromethylbenzene were then mixed thoroughly to obtain the second solution. The first and second solutions were then mixed thoroughly to obtain the deuterated reagent.

[0076] Magnesium borates are borates containing the element Mg, such as magnesium borate esters. Alkali metal salts are salts containing alkali metals, such as lithium salts, sodium salts, and potassium salts.

[0077] The coordination of boron (B) in magnesium boride compounds can be obtained by liquid NMR analysis of the electrolyte, such as... Figure 5 As shown, the 11B NMR spectrum exhibits a distinct and sharp single peak at a chemical shift of 1.56. This peak indicates that the boron element in the electrolyte exists in a tetracoordinate form and its coordination structure has not changed due to the introduction of lithium salt additives.

[0078] By using magnesium borides containing BO bonds and alkali metal salts as components of the electrolyte, an SEI film composed of alkali metal borides containing Mg and BO bonds can be formed in situ on the surface of the negative electrode in the battery. This alkali metal boride can effectively enhance the stability of the SEI film, giving the battery a lower overpotential, better cycle life, and higher specific capacity.

[0079] In some embodiments, the molar ratio of magnesium boride to alkali metal salt is 1:0.05~1.

[0080] The content of components (including magnesium borate and alkali metal salts) in the electrolyte can be determined using the following method: 500 μl of deuterated reagent is added to an NMR tube in a nitrogen-filled glove box. 100 μl of the non-aqueous electrolyte sample is then added to the NMR tube. The NMR tube is shaken to dissolve the non-aqueous electrolyte in the deuterated reagent. The analysis is performed using an Oxford Instruments X-Pulse benchtop NMR spectrometer. Because the non-aqueous electrolyte is highly sensitive to moisture, both the NMR analysis and sample preparation are conducted in a nitrogen atmosphere (H₂O content less than 0.1 ppm, O₂ content less than 0.1 ppm). Simultaneously, all instruments used in the analysis must be pre-washed with pure water and dried in a vacuum environment at 60°C for at least 48 hours. The deuterated reagent was prepared as follows: Deuterated dimethyl sulfoxide (DMSO-d6), deuterated acetonitrile, and trifluoromethylbenzene were dried using a 4A molecular sieve at a temperature above 25°C for at least 3 days, ensuring that the water content of all reagents was less than 3 ppm. A Metrohm 831 KF coulometric moisture analyzer was used for moisture testing. Then, in a nitrogen-filled glove box, 10 ml of dried DMSO-d6 and 300 μl of dried internal standard trifluoromethylbenzene were mixed thoroughly to obtain the first solution. 10 ml of dried deuterated acetonitrile and 300 μl of dried internal standard trifluoromethylbenzene were then mixed thoroughly to obtain the second solution. The first and second solutions were then mixed thoroughly to obtain the deuterated reagent.

[0081] By controlling the molar ratio of magnesium boride and alkali metal salt to 1:0.05~1, the stability of the SEI film can be enhanced, resulting in a battery with lower overpotential, better cycle life, and higher specific capacity.

[0082] For example, the molar ratio of magnesium boride to alkali metal salt can be 1:0.05, 1:0.10, 1:0.15, 1:0.20, 1:0.25, 1:0.30, 1:0.35, 1:0.40, 1:0.45, 1:0.50, 1:0.55, 1:0.60, 1:0.65, 1:0.70, 1:0.75, 1:0.80, 1:0.85, 1:0.90, 1:0.95, 1:1, etc., or any value within the range of 1:0.05 to 1.

[0083] In some embodiments, the molar concentration of the magnesium boride in the electrolyte is 0.1 mol / L to 0.8 mol / L. Exemplarily, the molar concentration of the magnesium boride in the electrolyte can be 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, 0.35 mol / L, 0.4 mol / L, 0.45 mol / L, 0.5 mol / L, 0.55 mol / L, 0.6 mol / L, 0.65 mol / L, 0.7 mol / L, 0.75 mol / L, 0.8 mol / L, etc., or any value within the range of 0.1 mol / L to 0.8 mol / L.

[0084] In some embodiments, the mass concentration of the alkali metal salt in the electrolyte is 0.01 mol / L to 0.5 mol / L. Exemplarily, the molar concentration of the alkali metal salt in the electrolyte can be 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, 0.35 mol / L, 0.4 mol / L, 0.45 mol / L, 0.5 mol / L, etc., or any value within the range of 0.01 mol / L to 0.5 mol / L.

[0085] In some embodiments, the magnesium boride is a magnesium borate ester. Optionally, the magnesium borate ester includes Mg[B(OR1)4]2 or Mg[B(OR2)]2. n (NR3) 4-n At least one of 2, wherein R1, R2 and R3 independently include at least one of ethyl, 2,2-difluoroethyl, 2,2,2-trifluoroethyl, 1-phenyl-2,2,2-trifluoroethyl, isopropyl, 1,3-dibromo-2-propyl, 1-phenylethyl, 3,3,3-trifluoropropyl, 1,1,1-trifluoro-2-propyl, hexafluoroisopropyl, perfluorotert-butyl, 2-trifluoromethyl-2-propyl, 3-perfluorobutylpropyl, 1,1,1,3,3,3-hexafluoro-2-phenyl-2-propyl, 2,2-bis(trifluoromethyl)propyl or tetrahydrofuranmethyl.

[0086] In some embodiments, the alkali metal salt includes at least one selected from lithium, sodium, or potassium salts. Optionally, the lithium salt includes at least one selected from lithium chloride, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium nitrate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl)imide, or lithium hydroxide. Optionally, the sodium salt includes at least one selected from sodium bis(fluorosulfonyl)imide, sodium hexafluorophosphate, sodium trifluoromethanesulfonate, or sodium bis(trifluoromethanesulfonyl)imide. Optionally, the potassium salt includes at least one selected from potassium bis(fluorosulfonyl)imide, potassium hexafluorophosphate, potassium trifluoromethanesulfonate, or potassium bis(trifluoromethanesulfonyl)imide.

[0087] In some embodiments, the magnesium borate ester is prepared by reacting a borate ester with a magnesium salt. Optionally, the borate ester includes at least one of trimethyl borate, triethyl borate, triisopropyl borate, tri-n-butyl borate, tris(2,2,2-trifluoroethyl) borate, hexafluoroborate, tris(pentafluorophenyl)borane, pinacol borane, pinacol borate, catechol borane, catechol borate, 1,8-naphthyldiaminoborate, MIDA borate, diethanolamine borate, bis(neopentylethylene glycol) diborate, bis(pinacol) diborate, bis(catechol) diborate, or pinacol diborate.

[0088] In some embodiments, the magnesium salt is prepared by reacting a magnesium source with a nucleophile.

[0089] Optionally, the magnesium source includes at least one of magnesium dihydrogenate, alkyl magnesium salt, or carboxyl magnesium salt. Further, the alkyl magnesium salt includes at least one of diethylmagnesium, di-n-butylmagnesium, di-sec-butylmagnesium, di-butyl(isopropyl)magnesium, di-n-butylethylmagnesium, or n-butyl-sec-butylmagnesium. The carboxyl magnesium salt includes at least one of magnesium formate, magnesium acetate, magnesium propionate, and / or magnesium formate.

[0090] Optionally, the nucleophile includes at least one of an alcohol, an acid, or an amine.

[0091] Furthermore, the alcohol compounds include at least one of monohydric alcohols or polyhydric alcohols. Monohydric alcohols include at least one of ethanol, difluoroethanol, trifluoroethanol, 1-phenyl-2,2,2-trifluoroethanol, isopropanol, 1,3-dibromo-2-propanol, 2-phenylisopropanol, trifluoropropanol, trifluoroisopropanol, hexafluoroisopropanol, perfluorotert-butanol, 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, or tetrahydrofuran-methanol. Polyol compounds include at least one of ethylene glycol, 2,3-butanediol, 2,3-diphenyl-2,3-butanediol, 2,3-dimethyl-2,3-butanediol, 1,2,4-butanetriol or hexafluoro-2,3-bis(trifluoromethyl)-2,3-butanediol.

[0092] Furthermore, the acid compounds include at least one of monobasic acid compounds or polybasic acid compounds. Monobasic acid compounds include at least one of formic acid, acetic acid, propionic acid, 2,2-dimethylpropionic acid, benzoic acid, phenylacetic acid, 2-hydroxy-2-phenylacetic acid, trifluoroacetic acid, valeric acid, hexanoic acid, octanoic acid, p-toluenesulfonic acid, p-methoxybenzoic acid, trifluoromethanesulfonic acid, fluorosulfonic acid, hydrochloric acid, or hexafluorophosphate. Polybasic acid compounds include at least one of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, maleic acid, trans-butenedioic acid, phthalic acid, isophthalic acid, terephthalic acid, 2,3-dihydroxysuccinic acid, 2-hydroxysuccinic acid, 2-hydroxypropane-1,2,3-tricarboxylic acid, isocitric acid, propene-1,2,3-tricarboxylic acid, trimesic acid, trimesic acid, ethylenediaminetetraacetic acid, inositol hexaphosphate, sulfuric acid, phosphoric acid, carbonic acid, sulfurous acid, boric acid, or silicic acid.

[0093] Furthermore, the amine compound preferably includes at least one of hexamethyldisilazane, hexaethyldisilazane, tris(trimethylsilyl)amine, N,N-bis(trimethylsilyl)methylamine, bis(trifluoromethanesulfonyl)imide, bis(fluorosulfonyl)imide, bis(pentafluoroethanesulfonyl)imide or bis(dimethylamino)tert-butylamine.

[0094] In other embodiments, the magnesium salts are commercially available. This application does not limit this.

[0095] In some embodiments, the electrolyte further includes a solvent, which includes at least one of an ether solvent or an amine solvent.

[0096] Optionally, the solvent may be at least one of chain ether solvents or cyclic ether solvents. Chain ether solvents include at least one of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, or tetraethylene glycol dimethyl ether. Cyclic ether solvents include at least one of tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, or 1,3-dioxolane.

[0097] Optionally, the amine solvent includes at least one of chain alkoxyamine solvents or cyclic alkoxyamine solvents. Chain alkoxyamine solvents include at least one of 2-methoxyethylamine, 2-ethoxyethylamine, 3-methoxypropylamine, 1-methoxy-2-propylamine, 2-(2-methoxyethoxy)ethylamine, N-(2-methoxyethyl)ethylamine, or 2-(dimethylamino)ethylmethyl ether. Cyclic alkoxyamine solvents include at least one of 2-(2-methoxyethyl)morpholine, 4-methoxymethylpiperidine, N-(2-methoxyethyl)tetrahydropyrrole, 3-methoxyazacyclobutane, or 2-(methoxymethyl)tetrahydrofuran-3-amine.

[0098] [Electrolyte preparation method] Having described the composition of the electrolyte, the preparation method of the electrolyte will now be described in detail.

[0099] Figure 1 This is a flowchart illustrating the methods provided in some embodiments of this application. Please refer to... Figure 1 This application provides a method for preparing an electrolyte, the method comprising: S100. A first reaction is carried out between a magnesium salt and a boride containing a BO bond to obtain a magnesium-containing boride.

[0100] In some embodiments, a magnesium salt is reacted with a boride having a BO bond in a solvent to obtain a magnesium-containing boride.

[0101] The reaction process is as follows: Mg-OR / Mg-NR + BO → Mg[B(OR)4]2 / Mg[B(OR) n (NR) 4-n ]2, wherein R includes at least one of ethyl, 2,2-difluoroethyl, 2,2,2-trifluoroethyl, 1-phenyl-2,2,2-trifluoroethyl, isopropyl, 1,3-dibromo-2-propyl, 1-phenylethyl, 3,3,3-trifluoropropyl, 1,1,1-trifluoro-2-propyl, hexafluoroisopropyl, perfluorotert-butyl, 2-trifluoromethyl-2-propyl, 3-perfluorobutylpropyl, 1,1,1,3,3,3-hexafluoro-2-phenyl-2-propyl, 2,2-bis(trifluoromethyl)propyl or tetrahydrofuranmethyl.

[0102] The borides containing BO bonds can be selected from one or more of the following: trimethyl borate, triethyl borate, triisopropyl borate, tri-n-butyl borate, tris(2,2,2-trifluoroethyl) borate, hexafluoroborate, tris(pentafluorophenyl)borane, pinacol borane, pinacol borate, catechol borane, catechol borate, 1,8-naphthyldiaminoborate, MIDA borate, diethanolamine borate, bis(neopentylethylene glycol) diborate, bis(pinacol) diborate, bis(catechol) diborate, and pinacol diborate; the purity of the borides containing BO bonds can be selected from 95% to 99.9%.

[0103] The solvent may be selected from hexamethyldisilazane, chain ethers, and / or cyclic ethers; the amine solvent may be selected from chain alkoxyamine solvents and / or cyclic alkoxyamine solvents; the chain ether may be selected from one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether; the cyclic ether may be selected from one or more of tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, and 1,3-dioxolane; the amine solvent may be selected from triethylamine, N,N-diisopropylethylamine, N-methylpyrrolidine, N-methylpiperidine, tris(2,2,2-trifluoroethyl)amine, N,N-dimethyltrifluoroethylamine, and hexamethyldisilazane. The solvent may be selected from one or more of the following: alkyl, bis(trimethylsilyl)methylamine, 2-methoxyethylamine, and diethylene glycolamine; chain-like alkoxyamine solvents may be selected from one or more of the following: 2-methoxyethylamine, 2-ethoxyethylamine, 3-methoxypropylamine, 1-methoxy-2-propylamine, 2-(2-methoxyethoxy)ethylamine, N-(2-methoxyethyl)ethylamine, and 2-(dimethylamino)ethylmethyl ether; cyclic alkoxyamine solvents may be selected from one or more of the following: 2-(2-methoxyethyl)morpholine, 4-methoxymethylpiperidine, N-(2-methoxyethyl)tetrahydropyrrole, 3-methoxyazacyclobutane, and 2-(methoxymethyl)tetrahydrofuran-3-amine. The purity of the organic solvent may be selected from 95% to 99.9%.

[0104] The molar ratio of magnesium salt to boride with BO bonds can be selected from 1:0.5 to 4.5; for example, the molar ratio of magnesium salt to boride with BO bonds can be 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, etc., or any value within the range of 1:0.5 to 4.5. The volume ratio of magnesium salt to solvent can be selected from 1 mmol:1.0 to 10.0 mL; for example, the volume ratio of magnesium salt to solvent can be 1 mmol:1.0 mL, 1 mmol:2.0 mL, 1 mmol:3.0 mL, 1 mmol:4.0 mL, 1 mmol:5.0 mL, 1 mmol:6.0 mL, 1 mmol:7.0 mL, 1 mmol:8.0 mL, 1 mmol:9.0 mL, 1 mmol:10.0 mL, etc., or any value within the range of 1 mmol:1.0 to 10.0 mL. The ratio of borides with BO bonds to solvent can be selected as 1 mmol: 0.5 to 20.0 mL; the ratio of borides with BO bonds to solvent can be 1 mmol: 0.5 mL, 1 mmol: 1.0 mL, 1 mmol: 2.0 mL, 1 mmol: 3.0 mL, 1 mmol: 4.0 mL, 1 mmol: 5.0 mL, 1 mmol: 6.0 mL, 1 mmol: 7.0 mL, 1 mmol: 8.0 mL, 1 mmol: 9.0 mL, 1 mmol: 10.0 mL, 1 mmol: 11.0 mL, 1 mmol: 12.0 mL, 1 mmol: 13.0 mL, 1 mmol: 14.0 mL, 1 mmol: 15.0 mL, 1 mmol: 16.0 mL, 1 mmol: 17.0 mL, 1 mmol: 18.0 mL, 1 mmol: 19.0 mL, 1 mmol: 20.0 mL, etc., or any value within the range of 1 mmol: 0.5 to 20.0 mL.

[0105] The mixing order of the magnesium salt, the BO bond-containing boride, and the solvent can be selected as follows: the BO bond-containing boride is added to the magnesium salt first, and then the solvent is added.

[0106] The reaction temperature of the first reaction can be selected from -70 to 180℃, the reaction time can be selected from 15 min to 48 h, and the pressure can be selected from 0 to 15 MPa; the reaction can be carried out under stirring conditions, and the stirring speed can be selected from 50 to 1500 rpm.

[0107] In some embodiments, after obtaining the magnesium boride, it is preferable to proceed directly to the next reaction without any post-processing.

[0108] S200. A magnesium boride and an alkali metal salt are mixed to obtain an electrolyte, which is a magnesium-ion battery electrolyte. The boron element in the magnesium boride exists in the electrolyte in a tetracoordinate form.

[0109] The reaction process is: Mg[B(OR)4]2 / Mg[B(OR) n (NR) 4-n ]2+M + →[Mg[B(OR)4]2 / Mg[B(OR) n (NR) 4-n ]2][M + ], wherein R includes at least one of ethyl, 2,2-difluoroethyl, 2,2,2-trifluoroethyl, 1-phenyl-2,2,2-trifluoroethyl, isopropyl, 1,3-dibromo-2-propyl, 1-phenylethyl, 3,3,3-trifluoropropyl, 1,1,1-trifluoro-2-propyl, hexafluoroisopropyl, perfluorotert-butyl, 2-trifluoromethyl-2-propyl, 3-perfluorobutylpropyl, 1,1,1,3,3,3-hexafluoro-2-phenyl-2-propyl, 2,2-bis(trifluoromethyl)propyl or tetrahydrofuranmethyl, and M includes an alkali metal element.

[0110] The alkali metal salt additives may be selected from lithium salts, sodium salts, and / or potassium salts; the lithium salts preferably include one or more of lithium chloride, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium nitrate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl)imide, and lithium hydroxide; the sodium salts may be selected from one or more of sodium bis(fluorosulfonyl)imide, sodium hexafluorophosphate, sodium trifluoromethanesulfonate, and sodium bis(trifluoromethanesulfonyl)imide; the potassium salts may be selected from one or more of potassium bis(fluorosulfonyl)imide, potassium hexafluorophosphate, potassium trifluoromethanesulfonate, and potassium bis(trifluoromethanesulfonyl)imide; the purity of the alkali metal salts is preferably 95% to 99.99%.

[0111] The ratio of magnesium borate to alkali metal salt can be selected as 1 mL: 0.05~1.0 mmol / L. For example, 1 mL: 0.05 mmol, 1 mL: 0.10 mmol, 1 mL: 0.15 mmol, 1 mL: 0.20 mmol, 1 mL: 0.25 mmol, 1 mL: 0.30 mmol, 1 mL: 0.35 mmol, 1 mL: 0.40 mmol, 1 mL: 0.45 mmol, 1 mL: 0.50 mmol, 1 mL: 0.55 mmol, 1 mL: 0.60 mmol, 1 mL: 0.65 mmol, 1 mL: 0.70 mmol, 1 mL: 0.75 mmol, 1 mL: 0.80 mmol, 1 mL: 0.85 mmol, 1 mL: 0.90 mmol, 1 mL: 0.95 mmol, 1 mL: 1.0 mmol, etc., can also be any value within the range of 0.05 to 1.0 mmol.

[0112] The mixing order of magnesium boride and alkali metal salt can be selected as adding alkali metal salt to magnesium boride.

[0113] The mixing time and temperature can be selected from -40 to 120℃, the mixing time can be selected from 1 min to 24 h, and the mixing pressure can be selected from 0 to 15 MPa; the mixing can be carried out under stirring conditions, and the stirring speed can be selected from 50 to 1500 rpm.

[0114] In some embodiments, after obtaining the electrolyte, it is preferable not to perform any post-processing and to directly apply it to subsequent applications.

[0115] This method uses a magnesium boride containing BO bonds and alkali metal salts to form an electrolyte. In the battery, an SEI film containing Mg and BO bonds as components can be formed in situ on the surface of the negative electrode. The alkali metal boride can effectively enhance the stability of the SEI film, so that the battery has a lower overpotential, better cycle life and higher specific capacity.

[0116] In some embodiments, the method for preparing magnesium salts includes: subjecting a magnesium source and a nucleophile to a second reaction to obtain magnesium salts.

[0117] For example, a magnesium source is reacted with a nucleophile in a second reaction, and the resulting product is subjected to vacuum distillation and drying to obtain a magnesium salt.

[0118] The magnesium source may be selected from magnesium dihydrogenate, alkyl magnesium salts and / or carboxyl magnesium salts; the alkyl magnesium salt may be selected from one or more of diethyl magnesium, di-n-butyl magnesium, di-sec-butyl magnesium, di-butyl(isopropyl) magnesium, di-n-butylethyl magnesium and n-butyl-sec-butyl magnesium; the carboxyl magnesium salt may be selected from one or more of magnesium formate, magnesium acetate, magnesium propionate and magnesium benzoate; the purity of the magnesium source is preferably 95% to 99.9%.

[0119] The nucleophile can be selected from alcohol sources, acid sources, and / or amine compounds; the alcohol source can be selected from monohydric alcohols and / or polyhydric alcohols; the acid source can be selected from monohydric acids and / or polyhydric acids; the monohydric alcohol can be selected from ethanol, difluoroethanol, trifluoroethanol, 1-phenyl-2,2,2-trifluoroethanol, isopropanol, 1,3-dibromo-2-propanol, 2-phenylisopropanol, trifluoropropanol, trifluoroisopropanol, hexafluoroisopropanol, perfluorotert-butanol, 2-trifluoromethyl-2-propanol, 3-perfluoromethyl-2-propanol, etc. One or more of fluorobutylpropanol, 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 may be 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 monocarboxylic acid compound may be formic acid. Acetic acid, propionic acid, 2,2-dimethylpropionic acid, benzoic acid, phenylacetic acid, 2-hydroxy-2-phenylacetic acid, trifluoroacetic acid, valeric acid, hexanoic acid, octanoic acid, p-toluenesulfonic acid, p-methoxybenzoic acid, trifluoromethanesulfonic acid, fluorosulfonic acid, hydrochloric acid, and hexafluorophosphate are selected as one or more of these compounds; the polybasic acid compounds may include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, maleic acid, trans-butenedioic acid, phthalic acid, isophthalic acid, terephthalic acid, 2,3-dihydroxysuccinic acid, 2-hydroxysuccinic acid, and 2-hydroxybutyric acid. The compound may be one or more of the following: propane-1,2,3-tricarboxylic acid, isocitric acid, propene-1,2,3-tricarboxylic acid, pyromellitic acid, trimellitic acid, ethylenediaminetetraacetic acid, inositol hexaphosphate, sulfuric acid, phosphoric acid, carbonic acid, sulfurous acid, boric acid, and silicic acid; the amine compound may be one or more of the following: hexamethyldisilazane, hexaethyldisilazane, tris(trimethylsilyl)amine, N,N-bis(trimethylsilyl)methylamine, bis(trifluoromethanesulfonyl)imide, bis(fluorosulfonyl)imide, bis(pentafluoroethanesulfonyl)imide, and bis(dimethylamino)tert-butylamine.

[0120] The molar ratio of magnesium source to nucleophile can be selected from 1.0:0.5 to 8.0. For example, the molar ratio of magnesium source to nucleophile can be 1.0:0.5, 1.0:1.0, 1.0:1.5, 1.0:2.0, 1.0:2.5, 1.0:3.0, 1.0:3.5, 1.0:4.0, 1.0:4.5, 1.0:5.0, 1.0:5.5, 1.0:6.0, 1.0:6.5, 1.0:7.0, 1.0:7.5, 1.0:8.0, etc., or any value within the range of 1.0:0.5 to 8.0.

[0121] The mixing order of the magnesium source and the nucleophile can be selected as follows: the nucleophile is slowly added to the magnesium source to carry out the reaction.

[0122] The reaction temperature of the second reaction can be selected from -80 to 140℃, the reaction time of the second reaction can be selected from 5 min to 72 h, and the pressure of the second reaction can be selected from 0 to 15 MPa.

[0123] The second reaction can be carried out under stirring conditions, and the stirring speed can be selected from 50 to 1500 rpm. The second reaction can be carried out in an atmospheric atmosphere or a protective atmosphere; the ambient humidity of the atmospheric atmosphere can be <70%; the protective atmosphere can be an inert atmosphere, or more specifically, argon.

[0124] The preferred temperature for vacuum distillation is 30~60℃, and the preferred time is 0.5~48h.

[0125] The drying process can be selected from vacuum drying and / or forced air drying; the drying temperature can be selected from -40 to 180℃, and the drying time can be selected from 0.5 to 72 hours.

[0126] In some embodiments, the magnesium source is preferably added in the form of a magnesium-containing organic solution; the solvent in the magnesium-containing organic solution preferably includes a nonpolar organic solvent and / or an ether-based organic solvent. This application does not impose any particular limitation on the concentration of the magnesium-containing organic solution; any concentration well known to those skilled in the art can be used.

[0127] In some embodiments, after obtaining the magnesium salt, it is preferable not to perform any post-processing and proceed directly to the next reaction.

[0128] [Battery cell] A battery pack may include a housing, end cap assemblies, and electrode assemblies. The housing has an opening, the electrode assemblies are housed within the housing, and the end cap assemblies are used to seal the opening.

[0129] The shape of the outer casing can be determined based on the specific shape of the electrode assembly. For example, if the electrode assembly is a cuboid structure, the outer casing can also be a cuboid structure.

[0130] The outer shell can be made of various materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, etc. This application embodiment does not impose any special restrictions on this.

[0131] The end cap assembly includes an end cap and electrode terminals. The end cap assembly seals the opening of the housing to form a sealed mounting space for accommodating the electrode assembly. The mounting space also accommodates an electrolyte, such as an electrolyte solution. As the component that outputs electrical energy from the electrode assembly, the end cap assembly's electrode terminals are used for electrical connection to the electrode assembly; specifically, the electrode terminals are electrically connected to the tabs of the electrode assembly. For example, the electrode terminals and tabs are connected via a current collector to achieve this electrical connection.

[0132] It should be noted that the housing can have one or two openings. If the housing has one opening, there can also be one end cap assembly, which can contain two electrode terminals for electrical connection to the positive and negative electrodes of the electrode assembly, respectively. If the housing has two openings, for example, on opposite sides of the housing, there can also be two end cap assemblies, each covering one of the openings. In this case, one end cap assembly can have a positive electrode terminal for electrical connection to the positive electrode of the electrode assembly, while the other end cap assembly can have a negative electrode terminal for electrical connection to the negative electrode of the electrode assembly.

[0133] In some embodiments, the battery cell may further include an insulating protective member fixed to the outer periphery of the electrode assembly, the insulating protective member serving to insulate and isolate the electrode assembly from the housing. Exemplarily, the insulating protective member is adhesive tape bonded to the outer periphery of the electrode assembly. In some embodiments, there are multiple electrode assemblies, and the insulating protective member surrounds the outer periphery of multiple electrode assemblies, forming a single integral structure to maintain the structural stability of the electrode assembly.

[0134] The electrode assembly includes electrode sheets and a separator. The electrode sheets include positive electrode sheets and negative electrode sheets. The electrode assembly can be a wound electrode assembly or a stacked electrode assembly, and the embodiments of this application are not limited thereto.

[0135] The positive electrode includes a positive current collector and a positive electrode film layer. The positive electrode film layer is coated on the surface of the positive current collector. The positive current collector without the positive electrode film layer protrudes from the positive current collector with the positive electrode film layer. The positive current collector without the positive electrode film layer serves as the positive electrode tab. The positive electrode film layer includes a positive electrode active material layer.

[0136] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0137] The negative electrode sheet includes a negative current collector and a negative electrode film layer. The negative electrode film layer is coated on the surface of the negative current collector. The negative current collector without the negative electrode film layer protrudes from the negative current collector with the negative electrode film layer. The negative current collector without the negative electrode film layer serves as the negative electrode tab. The negative electrode film layer includes a negative electrode active material layer.

[0138] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0139] In some embodiments, the negative electrode active material layer includes a negative electrode active material, which may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, and tin-based materials. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0140] In some embodiments, the negative electrode active material layer may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0141] In some embodiments, the negative electrode active material layer may also optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0142] In some implementations, in order to reduce the probability of melting due to high current, the number of positive electrode tabs is multiple and stacked together, and the number of negative electrode tabs is multiple and stacked together.

[0143] This application does not impose any particular restrictions on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0144] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polytetrafluoroethylene. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0145] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0146] In some embodiments, the electrolyte is the aforementioned electrolyte solution.

[0147] In some embodiments, the battery cell includes a negative electrode sheet, at least a portion of the surface of which is covered with an SEI film. The SEI film comprises an alkali metal borate, the alkali metal borate containing Mg, and the alkali metal borate having BO bonds. The composition of the SEI can be obtained by testing the surface of the negative electrode sheet using methods such as XPS.

[0148] In some embodiments, the alkali metal boride includes Mg[B(OR4)4]2[M + ] or Mg[B(OR5) n (NR6) 4-n ]2[M + At least one of the following, wherein R4, R5 and R6 independently include at least one of ethyl, 2,2-difluoroethyl, 2,2,2-trifluoroethyl, 1-phenyl-2,2,2-trifluoroethyl, isopropyl, 1,3-dibromo-2-propyl, 1-phenylethyl, 3,3,3-trifluoropropyl, 1,1,1-trifluoro-2-propyl, hexafluoroisopropyl, perfluorotert-butyl, 2-trifluoromethyl-2-propyl, 3-perfluorobutylpropyl, 1,1,1,3,3,3-hexafluoro-2-phenyl-2-propyl, 2,2-bis(trifluoromethyl)propyl or tetrahydrofuranmethyl.

[0149] In some embodiments, the battery cell is a magnesium-ion battery, such as a magnesium oxide battery, a magnesium sulfide battery, a magnesium sulfide battery, or a magnesium organic battery.

[0150] [Preparation methods for battery cells] Having introduced the structure of the battery cell, the following section will describe the preparation method of the battery cell in detail.

[0151] The method for preparing a single battery cell provided in this application includes the following steps: S100. The active material is prepared into an active slurry and coated on the surface of the current collector to obtain an electrode sheet.

[0152] The coating method can be: scraping, roller coating, slot coating, etc., and this application does not limit it.

[0153] S200. Assemble the electrode plates and the separator, and bring the electrolyte into contact with at least a portion of the electrode plates and the separator to obtain a battery cell.

[0154] The assembly of the positive electrode, separator, and negative electrode can be either wound or stacked. Specifically, the separator, positive electrode, separator, and negative electrode are stacked sequentially, wound to form a wound flat structure, and then hot-pressed to obtain a wound electrode assembly; or, after preparing the positive electrode, the positive electrode, separator, negative electrode, separator, and so on are stacked sequentially to form a stacked electrode assembly.

[0155] [Rechargeable Battery] In this application, a secondary battery can refer to a single battery cell, or it can refer to a single physical module comprising multiple battery cells to provide higher voltage and capacity, which can be in the form of a battery pack, battery module, etc. A secondary battery may include a housing for encapsulating multiple battery cells, the housing preventing liquids or other foreign matter from affecting the charging or discharging of the battery cells.

[0156] A secondary battery consists of a casing and individual battery cells, with the individual battery cells housed within the casing.

[0157] The housing provides a space to house individual battery cells. In some embodiments, the housing may include a first part and a second part, which overlap each other to define a space for accommodating the battery cells. The connection between the first and second parts can be sealed using a sealant, such as a sealing ring or sealant.

[0158] The first and second parts can have various shapes, such as cuboids or cylinders. The first part can be a hollow structure with an opening on one side to form a cavity for accommodating individual battery cells, and the second part can also be a hollow structure with an opening on one side to form a cavity for accommodating individual battery cells. The opening side of the second part covers the opening side of the first part, thus forming a box with accommodating space. Alternatively, the first part can be a hollow structure with an opening on one side, and the second part can be a plate-like structure, with the second part covering the opening side of the first part, thus forming a box with accommodating space.

[0159] In a secondary battery, there can be one or more individual battery cells. If there are multiple individual cells, they can be connected in series, parallel, or a combination thereof. A combination thereof means that multiple individual cells are connected in both series and parallel configurations. Multiple individual cells can be directly connected in series, parallel, or a combination thereof, and then the entire assembly of these cells is housed within a casing. Alternatively, multiple individual cells can first be connected in series, parallel, or a combination thereof to form a battery module, and then these modules can be connected in series, parallel, or a combination thereof to form a single unit, which is then housed within a casing. Individual battery cells can be cylindrical, flat, cuboid, or other shapes.

[0160] In some embodiments, the secondary battery may further include a busbar component, through which multiple battery cells can be electrically connected to each other to achieve series, parallel, or mixed connection of multiple battery cells.

[0161] The battery cell or secondary battery can be used in electrical devices such as vehicles, ships, or aircraft. A power system for such an electrical device can be constructed using the battery cells disclosed in this application.

[0162] [Electrical appliances] This application provides an electrical device that uses a battery as a power source. The electrical device can be, but is not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0163] The following examples will describe one or more embodiments in more detail. Of course, these examples do not limit the scope of the one or more embodiments.

[0164] Example 1 An electrolyte, the preparation process of which is as follows: The raw materials were measured according to the following amounts: di-n-butylmagnesium hexane solution (containing 20 mmol of di-n-butylmagnesium); 50 mmol of bis(trifluoromethanesulfonyl)imide; 30 mmol of triethyl borate; 40.0 mL of 99.0% 2-methoxyethylamine solvent; and 4 mmol of 99% sodium bis(trifluoromethanesulfonyl)imide.

[0165] (1) Under atmospheric conditions (ambient humidity < 70%), bis(trifluoromethanesulfonyl)imide was first slowly added to di-n-butylmagnesium hexane solution, with a stirring speed of 300 rpm, a reaction temperature of 5℃, a pressure of 0.2 MPa, and a reaction time of 60 min. After the reaction was completed, the solution was distilled under reduced pressure at 30℃ for 60 min and dried under vacuum at 60℃ for 12 h to obtain magnesium salt.

[0166] (2) Add magnesium salt and triethyl borate to 2-methoxyethylamine solvent and stir to react. The stirring speed is 500 rpm, the reaction temperature is 20℃, the pressure is 0.2 MPa, and the reaction time is 240 min to obtain magnesium borate.

[0167] (3) Add sodium bis(trifluoromethanesulfonyl)imide to the magnesium borate, stir at 350 rpm, react at 30°C, pressurize at 0.2 MPa, and react for 90 min to obtain the electrolyte.

[0168] Example 2 An electrolyte, the preparation process of which is as follows: The raw materials were measured according to the following amounts: di-sec-butylmagnesium hexane solution (containing 25 mmol of di-sec-butylmagnesium); 50 mmol of bis(fluorosulfonyl)imide; 40 mmol of trimethyl borate; 50.0 mL of 99.0% diethylene glycol dimethyl ether solvent; and 10 mmol of 99% potassium bis(trifluoromethanesulfonyl)imide.

[0169] (1) Under atmospheric conditions (ambient humidity < 70%), difluorosulfonamide was first slowly added to di-sec-butylmagnesium hexane solution, with a stirring speed of 600 rpm, a reaction temperature of 0℃, a pressure of 0.3 MPa, and a reaction time of 120 min. After the reaction was completed, the solution was distilled under reduced pressure at 20℃ for 120 min and dried under vacuum at 50℃ for 24 h to obtain magnesium salt.

[0170] (2) Add magnesium salt and trimethyl borate to diethylene glycol dimethyl ether solvent and stir to react. The stirring speed is 300 rpm, the reaction temperature is 25℃, the pressure is 0.3 MPa, and the reaction time is 240 min to obtain magnesium borate.

[0171] (3) Add potassium bis(trifluoromethanesulfonyl)imide to the magnesium borate, stir at 350 rpm, react at 30°C, pressurize at 0.3 MPa, and react for 120 min to obtain the electrolyte.

[0172] Example 3 An electrolyte, the preparation process of which is as follows: The raw materials are measured according to the following amounts: diethylmagnesium hexane solution (containing 10 mmol of diethylmagnesium); 20 mmol of hexafluoroisopropanol; 15 mmol of hexafluoroborate; 30.0 mL of 99.5% ethylene glycol dimethyl ether solvent; and 5 mmol of 99% anhydrous lithium chloride.

[0173] (1) In an atmospheric environment (ambient humidity < 70%), hexafluoroisopropanol was first slowly added to diethylmagnesium hexane solution, with a stirring speed of 400 rpm, a reaction temperature of -5℃, a pressure of 0.3 MPa, and a reaction time of 30 min. After the reaction was completed, the solution was distilled under reduced pressure at 0℃ for 120 min and dried under vacuum at 60℃ for 12 h to obtain magnesium salt.

[0174] (2) Add magnesium salt and hexafluoroborate to ethylene glycol dimethyl ether solvent and stir to react. The stirring speed is 300 rpm, the reaction temperature is 10℃, the pressure is 0.3 MPa, and the reaction time is 60 min to obtain magnesium borate.

[0175] (3) Add anhydrous lithium chloride to the magnesium boride, stir at 350 rpm, react at 20°C, pressurize at 0.3 MPa, and react for 10 min to obtain the electrolyte.

[0176] Example 4 An electrolyte, the preparation process of which is as follows: The raw materials are measured according to the following amounts: diethylmagnesium hexane solution (containing 10 mmol of diethylmagnesium); 20 mmol of hexafluoroisopropanol; 15 mmol of hexafluoroborate; 30.0 mL of 99.5% ethylene glycol dimethyl ether solvent; and 0.5 mmol of 99% anhydrous lithium chloride.

[0177] (1) In an atmospheric environment (ambient humidity < 70%), hexafluoroisopropanol was first slowly added to diethylmagnesium hexane solution, with a stirring speed of 400 rpm, a reaction temperature of -5℃, a pressure of 0.3 MPa, and a reaction time of 30 min. After the reaction was completed, the solution was distilled under reduced pressure at 0℃ for 120 min and dried under vacuum at 60℃ for 12 h to obtain magnesium salt.

[0178] (2) Add magnesium salt and hexafluoroborate to ethylene glycol dimethyl ether solvent and stir to react. The stirring speed is 300 rpm, the reaction temperature is 10℃, the pressure is 0.3 MPa, and the reaction time is 60 min to obtain magnesium borate.

[0179] (3) Add anhydrous lithium chloride to the magnesium boride, stir at 350 rpm, react at 20°C, pressurize at 0.3 MPa, and react for 10 min to obtain the electrolyte.

[0180] Example 5 An electrolyte, the preparation process of which is as follows: The raw materials are measured according to the following amounts: diethylmagnesium hexane solution (containing 5 mmol of diethylmagnesium); hexafluoroisopropanol 10 mmol; hexafluoroborate 7.5 mmol; 99.5% ethylene glycol dimethyl ether solvent 15.0 mL; and 99% anhydrous lithium chloride 5 mmol.

[0181] (1) In an atmospheric environment (ambient humidity < 70%), hexafluoroisopropanol was first slowly added to diethylmagnesium hexane solution, with a stirring speed of 400 rpm, a reaction temperature of -5℃, a pressure of 0.3 MPa, and a reaction time of 30 min. After the reaction was completed, the solution was distilled under reduced pressure at 0℃ for 120 min and dried under vacuum at 60℃ for 12 h to obtain magnesium salt.

[0182] (2) Add magnesium salt and hexafluoroborate to ethylene glycol dimethyl ether solvent and stir to react. The stirring speed is 300 rpm, the reaction temperature is 10℃, the pressure is 0.3 MPa, and the reaction time is 60 min to obtain magnesium borate.

[0183] (3) Add anhydrous lithium chloride to the magnesium boride, stir at 350 rpm, react at 20°C, pressurize at 0.3 MPa, and react for 10 min to obtain the electrolyte.

[0184] Example 6 An electrolyte, the preparation process of which is as follows: The raw materials are measured according to the following amounts: diethylmagnesium hexane solution (containing 10 mmol of diethylmagnesium); 20 mmol of hexafluoroisopropanol; 15 mmol of hexafluoroborate; 30.0 mL of 99.5% tetraethylene glycol dimethyl ether solvent; and 5 mmol of 99% anhydrous lithium chloride.

[0185] (1) In an atmospheric environment (ambient humidity < 70%), hexafluoroisopropanol was first slowly added to diethylmagnesium hexane solution, with a stirring speed of 400 rpm, a reaction temperature of -5℃, a pressure of 0.3 MPa, and a reaction time of 30 min. After the reaction was completed, the solution was distilled under reduced pressure at 0℃ for 120 min and dried under vacuum at 60℃ for 12 h to obtain magnesium salt.

[0186] (2) Add magnesium salt and hexafluoroborate to ethylene glycol dimethyl ether solvent and stir to react. The stirring speed is 300 rpm, the reaction temperature is 10℃, the pressure is 0.3 MPa, and the reaction time is 60 min to obtain magnesium borate.

[0187] (3) Add anhydrous lithium chloride to the magnesium boride, stir at 350 rpm, react at 20°C, pressurize at 0.3 MPa, and react for 10 min to obtain the electrolyte.

[0188] Example 7 An electrolyte, the preparation process of which is as follows: The raw materials are measured according to the following amounts: diethylmagnesium hexane solution (containing 10 mmol of diethylmagnesium); 20 mmol of hexafluoroisopropanol; 15 mmol of hexafluoroborate; 30.0 mL of 99.5% tetrahydrofuran solvent; and 5 mmol of 99% anhydrous lithium chloride.

[0189] (1) In an atmospheric environment (ambient humidity < 70%), hexafluoroisopropanol was first slowly added to diethylmagnesium hexane solution, with a stirring speed of 400 rpm, a reaction temperature of -5℃, a pressure of 0.3 MPa, and a reaction time of 30 min. After the reaction was completed, the solution was distilled under reduced pressure at 0℃ for 120 min and dried under vacuum at 60℃ for 12 h to obtain magnesium salt.

[0190] (2) Add magnesium salt and hexafluoroborate to ethylene glycol dimethyl ether solvent and stir to react. The stirring speed is 300 rpm, the reaction temperature is 10℃, the pressure is 0.3 MPa, and the reaction time is 60 min to obtain magnesium borate.

[0191] (3) Add anhydrous lithium chloride to the magnesium boride, stir at 350 rpm, react at 20°C, pressurize at 0.3 MPa, and react for 10 min to obtain the electrolyte.

[0192] Comparative Example 1 An electrolyte, the preparation process of which is as follows: The raw materials were measured according to the following amounts: di-n-butylmagnesium hexane solution (containing 20 mmol of di-n-butylmagnesium); 50 mmol of bis(trifluoromethanesulfonyl)imide; and 40.0 mL of 99.0% 2-methoxyethylamine solvent.

[0193] (1) Under atmospheric conditions (ambient humidity < 70%), bis(trifluoromethanesulfonyl)imide was first slowly added to di-n-butylmagnesium hexane solution, with a stirring speed of 300 rpm, a reaction temperature of 5℃, a pressure of 0.2 MPa, and a reaction time of 60 min. After the reaction was completed, the solution was distilled under reduced pressure at 30℃ for 60 min and dried under vacuum at 60℃ for 12 h to obtain magnesium salt.

[0194] (2) Add magnesium salt to 2-methoxyethylamine solvent and stir to react. The stirring speed is 500 rpm, the reaction temperature is 20℃, the pressure is 0.2 MPa, and the reaction time is 240 min to obtain electrolyte.

[0195] Comparative Example 2 An electrolyte, the preparation process of which is as follows: The raw materials were measured according to the following amounts: di-sec-butylmagnesium hexane solution (containing 25 mmol of di-sec-butylmagnesium); 50 mmol of bis(fluorosulfonyl)imide; and 50.0 mL of 99.0% diethylene glycol dimethyl ether solvent.

[0196] (1) Under atmospheric conditions (ambient humidity < 70%), difluorosulfonamide was first slowly added to di-sec-butylmagnesium hexane solution, with a stirring speed of 600 rpm, a reaction temperature of 0℃, a pressure of 0.3 MPa, and a reaction time of 120 min. After the reaction was completed, the solution was distilled under reduced pressure at 20℃ for 120 min and dried under vacuum at 50℃ for 24 h to obtain magnesium salt.

[0197] (2) Add magnesium salt to diethylene glycol dimethyl ether solvent and stir to react. The stirring speed is 300 rpm, the reaction temperature is 25℃, the pressure is 0.3 MPa, and the reaction time is 240 min to obtain electrolyte.

[0198] Comparative Example 3 An electrolyte, the preparation process of which is as follows: The raw materials were measured according to the following quantities: diethylmagnesium hexane solution (containing 10 mmol of diethylmagnesium); 20 mmol of hexafluoroisopropanol; and 30.0 mL of 99.5% ethylene glycol dimethyl ether solvent.

[0199] (1) In an atmospheric environment (ambient humidity < 70%), hexafluoroisopropanol was first slowly added to diethylmagnesium hexane solution, with a stirring speed of 400 rpm, a reaction temperature of -5℃, a pressure of 0.3 MPa, and a reaction time of 30 min. After the reaction was completed, the solution was distilled under reduced pressure at 0℃ for 120 min and dried under vacuum at 60℃ for 12 h to obtain magnesium salt.

[0200] (2) Add magnesium salt to ethylene glycol dimethyl ether solvent and stir to react. The stirring speed is 300 rpm, the reaction temperature is 10℃, the pressure is 0.3 MPa, and the reaction time is 60 min to obtain electrolyte.

[0201] Comparative Example 4 An electrolyte, the preparation process of which is as follows: The raw materials are measured according to the following amounts: diethylmagnesium hexane solution (containing 10 mmol of diethylmagnesium); 20 mmol of hexafluoroisopropanol; 0.003 mmol of hexafluoroborate; 30.0 mL of 99.5% ethylene glycol dimethyl ether solvent; and 5 mmol of 99% anhydrous lithium chloride.

[0202] (1) In an atmospheric environment (ambient humidity < 70%), hexafluoroisopropanol was first slowly added to diethylmagnesium hexane solution, with a stirring speed of 400 rpm, a reaction temperature of -5℃, a pressure of 0.3 MPa, and a reaction time of 30 min. After the reaction was completed, the solution was distilled under reduced pressure at 0℃ for 120 min and dried under vacuum at 60℃ for 12 h to obtain magnesium salt.

[0203] (2) Add magnesium salt and hexafluoroborate to ethylene glycol dimethyl ether solvent and stir to react. The stirring speed is 300 rpm, the reaction temperature is 10℃, the pressure is 0.3 MPa, and the reaction time is 60 min to obtain magnesium borate.

[0204] (3) Add anhydrous lithium chloride to the magnesium boride, stir at 350 rpm, react at 20°C, pressurize at 0.3 MPa, and react for 10 min to obtain the electrolyte.

[0205] Comparative Example 5 An electrolyte, the preparation process of which is as follows: The raw materials are measured according to the following amounts: diethylmagnesium hexane solution (containing 10 mmol of diethylmagnesium); 20 mmol of hexafluoroisopropanol; 0.05 mmol of hexafluoroborate; 30.0 mL of 99.5% ethylene glycol dimethyl ether solvent; and 5 mmol of 99% anhydrous lithium chloride.

[0206] (1) In an atmospheric environment (ambient humidity < 70%), hexafluoroisopropanol was first slowly added to diethylmagnesium hexane solution, with a stirring speed of 400 rpm, a reaction temperature of -5℃, a pressure of 0.3 MPa, and a reaction time of 30 min. After the reaction was completed, the solution was distilled under reduced pressure at 0℃ for 120 min and dried under vacuum at 60℃ for 12 h to obtain magnesium salt.

[0207] (2) Add magnesium salt and hexafluoroborate to ethylene glycol dimethyl ether solvent and stir to react. The stirring speed is 300 rpm, the reaction temperature is 10℃, the pressure is 0.3 MPa, and the reaction time is 60 min to obtain magnesium borate.

[0208] (3) Add anhydrous lithium chloride to the magnesium boride, stir at 350 rpm, react at 20°C, pressurize at 0.3 MPa, and react for 10 min to obtain the electrolyte.

[0209] Test Example 1 The electrolytes provided in Examples 1 to 3, Comparative Examples 1 to 3, and Comparative Example 5 were respectively assembled into magnesium-magnesium symmetric batteries. The assembly process was as follows: the negative electrode shell, spring, gasket, magnesium sheet, GF / D glass fiber separator, magnesium sheet, and positive electrode shell were assembled in that order. 100 microliters of electrolyte were added to each battery to wet the separator. Finally, the battery was sealed and formed.

[0210] XPS elemental analysis was performed on the SEI film on the surface of the magnesium metal anode of the magnesium-magnesium symmetric battery formed by the electrolytes provided in Examples 1 to 3. The results are as follows: Figures 2 to 4 As shown. Among them, Figure 2 The figure shows the XPS elemental analysis of the SEI film on the surface of the magnesium metal anode after the electrolyte prepared in Example 1 was cycled in a magnesium symmetric battery. As can be seen from the figure, sodium and BO bonds are present in the SEI film on the surface of the magnesium metal anode, indicating that the electrolyte induces the formation of an SEI film containing alkali metal borate esters on the surface of the magnesium metal anode. Figure 3 The image shows the XPS elemental analysis of the SEI film on the magnesium metal anode surface after cycling the electrolyte prepared in Example 2 in a magnesium symmetric battery. The presence of potassium and BO bonds in the SEI film indicates that the electrolyte induced the formation of an SEI film containing alkali metal borate esters on the magnesium metal anode surface. Figure 4 The image shows the XPS elemental analysis of the SEI film on the magnesium metal anode surface after cycling the electrolyte prepared in Example 3 in a magnesium symmetric battery. The presence of lithium and BO bonds in the SEI film indicates that the electrolyte induced the formation of an SEI film containing alkali metal borate esters on the magnesium metal anode surface.

[0211] Liquid NMR spectroscopy was performed on the electrolyte of Example 3, and the results are as follows: Figure 5As shown in the figure, the 11B NMR spectrum exhibits a distinct and sharp single peak at a chemical shift of 1.56. This peak indicates that the boron element in the electrolyte exists in a four-coordinated form and its coordination structure has not changed due to the introduction of lithium salt additives. This result is a key feature for understanding the structure of the electrolyte components, and the one-dimensional NMR spectra of other elements further support this conclusion.

[0212] SEM tests were performed on the surface of the magnesium metal anode of the magnesium-magnesium symmetric battery assembled with the electrolyte provided in Example 3. The results are as follows: Figure 6 As shown in the figure, the alkali metal borate ester-based SEI film formed on the surface of the magnesium metal anode has a uniform morphology.

[0213] Overpotential-time tests were performed on magnesium-magnesium symmetric batteries formed with the electrolytes provided in Examples 1 to 3, Comparative Examples 1 to 3, and Comparative Example 5. The test procedure was as follows: the batteries were first left to rest for 5 minutes, then subjected to an overpotential-time test at 1 mA / cm². 2 The current density was used to test the cycling performance.

[0214] Test results are as follows Figure 7 , Figure 8 , Figure 9 and Figure 10 As shown. Figure 7 The electrolytes provided for Example 1 and Comparative Example 1 were at 1 mA / cm 2 Cycle performance of magnesium-magnesium symmetric cells at current density; Figure 8 The electrolytes provided for Example 2 and Comparative Example 2 were at 1 mA / cm 2 Cycle performance of magnesium-magnesium symmetric cells at current density; Figure 9 The electrolytes provided for Example 3 and Comparative Example 3 were at 1 mA / cm 2 Cycle performance of magnesium-magnesium symmetric cells at current density; Figure 10 The electrolyte provided for Comparative Example 5 was at 1 mA / cm 2 Cycle performance of magnesium-magnesium symmetric cells at current density. From Figure 7-10 The symmetric cell test results showed that the battery formed by the electrolyte provided in the embodiments of this application has good cycle performance and generally lower overpotential than the battery formed by the electrolyte provided in the comparative example.

[0215] Test Example 2 The electrolytes provided in Examples 3 to 7 and Comparative Examples 3 to 5 were respectively assembled into magnesium oxide batteries. The assembly process was as follows: the negative electrode shell, spring sheet, gasket, magnesium sheet, GF / D glass fiber separator, MnO2 positive electrode, and positive electrode shell were assembled in that order. 100 microliters of electrolyte were added to each battery to wet the separator. Finally, the battery was encapsulated and formed.

[0216] The specific capacity-voltage performance of magnesium oxide batteries was tested. The test procedure was as follows: the batteries were first left to rest for 4 hours, and then the specific capacity-voltage performance was tested at a current density of 50 mA / g.

[0217] Test results are as follows Figure 11 , Figure 12 , Figure 13 As shown in Table 1, Figure 11 The specific capacity-voltage performance of magnesium oxide full cells with the electrolyte provided in Comparative Example 3 at a current density of 50 mA / g. Figure 12 The specific capacity-voltage performance of the magnesium oxide full cell with the electrolyte provided in Example 3 at a current density of 50 mA / g; Figure 13 The specific capacity-voltage performance of the magnesium oxide battery with the electrolyte provided in Comparative Example 5 at a current density of 50 mA / g.

[0218] Table 1

[0219] Depend on Figure 11 , Figure 12 and Figure 13 As shown in Table 1, the electrolyte provided in the embodiments of this application, combined with magnesium sulfide batteries, has a higher specific capacity (up to 169 mAh / g) and better cycle performance (>100 cycles).

[0220] The electrolytes provided in Examples 3 to 7 and Comparative Examples 3 to 5 were respectively assembled into magnesium sulfide batteries. The assembly process was as follows: the negative electrode shell, spring sheet, gasket, magnesium sheet, GF / D glass fiber separator, vanadium-based sulfide positive electrode, and positive electrode shell were assembled in that order. 100 microliters of electrolyte were added to each battery to wet the separator. Finally, the battery was encapsulated and formed.

[0221] The specific capacity-voltage performance of magnesium sulfide batteries was tested. The test procedure was as follows: the batteries were first left to rest for 4 hours, and then the specific capacity-voltage performance was tested at a current density of 200 mA / g.

[0222] Test results are as follows Figure 14 , Figure 15 , Figure 16 As shown in Table 2, Figure 14 The specific capacity-voltage performance of the magnesium sulfide full cell with the electrolyte provided in Comparative Example 3 at a current density of 200 mA / g. Figure 15 The specific capacity-voltage performance of the magnesium sulfide full cell with the electrolyte provided in Example 3 at a current density of 200 mA / g; Figure 16 The specific capacity-voltage performance of the magnesium sulfide battery provided in Comparative Example 5 at a current density of 200 mA / g.

[0223] Table 2

[0224] Depend on Figure 14 , Figure 15 and Figure 16 As shown in Table 2, the electrolyte provided in the embodiments of this application, combined with magnesium sulfide batteries, has a higher specific capacity (up to 295 mAh / g).

[0225] The electrolytes provided in Examples 3 to 7 and Comparative Examples 3 to 5 were respectively assembled into magnesium-sulfur batteries. The assembly process was as follows: the negative electrode shell, spring sheet, gasket, magnesium sheet, GF / D glass fiber separator, sulfur positive electrode, and positive electrode shell were assembled in that order. 100 microliters of electrolyte were added to each battery to wet the separator. Finally, the battery was sealed and formed.

[0226] The specific capacity-voltage performance of the magnesium-sulfur battery was tested. The test procedure was as follows: the battery was first left to rest for 12 hours, and then the specific capacity-voltage performance was tested at a current density of 167.5 mA / g.

[0227] Test results are as follows Figure 17 , Figure 18 , Figure 19 As shown in Table 3, Figure 17 The specific capacity-voltage performance of the magnesium-sulfur battery provided in Comparative Example 3 at a current density of 167.5 mA / g; Figure 18 The specific capacity-voltage performance of the magnesium-sulfur battery provided in Example 3 at a current density of 167.5 mA / g; Figure 19 The specific capacity-voltage performance of the magnesium-sulfur battery provided in Comparative Example 5 at a current density of 167.5 mA / g.

[0228] Table 3

[0229] Depend on Figure 17 , Figure 18 and Figure 19 As shown in Table 3, the electrolyte provided in the embodiments of this application, when used with magnesium-sulfur batteries, has a higher specific capacity (up to 1200 mAh / g) and better cycle performance (>200 cycles).

[0230] The above are merely specific embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An electrolyte, characterized in that, The electrolyte is a magnesium-ion battery electrolyte, which includes magnesium boride and alkali metal salt. The magnesium boride has BO bonds, and the B element in the magnesium boride exists in the electrolyte in a tetracoordinate form.

2. The electrolyte according to claim 1, characterized in that, The molar ratio of the magnesium boride to the alkali metal salt is 1:0.05~1.

3. The electrolyte according to claim 1, characterized in that, The molar concentration of the magnesium boride in the electrolyte is 0.1 mol / L to 0.8 mol / L; and / or The molar concentration of the alkali metal salt in the electrolyte is 0.01 mol / L to 0.5 mol / L.

4. The electrolyte according to any one of claims 1 to 3, characterized in that, The magnesium borate is a magnesium borate ester; and / or The alkali metal salt includes at least one of lithium, sodium, or potassium salts.

5. The electrolyte according to claim 4, characterized in that, The magnesium borate ester includes Mg[B(OR1)4]2 or Mg[B(OR2)2. n (NR3) 4-n At least one of R1, R2, and R3, wherein R1, R2, and R3 each independently comprise at least one of ethyl, 2,2-difluoroethyl, 2,2,2-trifluoroethyl, 1-phenyl-2,2,2-trifluoroethyl, isopropyl, 1,3-dibromo-2-propyl, 1-phenylethyl, 3,3,3-trifluoropropyl, 1,1,1-trifluoro-2-propyl, hexafluoroisopropyl, perfluorotert-butyl, 2-trifluoromethyl-2-propyl, 3-perfluorobutylpropyl, 1,1,1,3,3,3-hexafluoro-2-phenyl-2-propyl, 2,2-bis(trifluoromethyl)propyl, or tetrahydrofuranmethyl; and / or The lithium salt comprises at least one of lithium chloride, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium nitrate, lithium trifluoromethanesulfonate, lithium bis(fluoromethanesulfonyl)imide, or lithium hydroxide; and / or The sodium salt comprises at least one of sodium bis(fluorosulfonyl)imide, sodium hexafluorophosphate, sodium trifluoromethanesulfonate, or sodium bis(trifluoromethanesulfonyl)imide; and / or The potassium salt includes at least one of potassium bis(fluorosulfonyl)imide, potassium hexafluorophosphate, potassium trifluoromethanesulfonate, or potassium bis(trifluoromethanesulfonyl)imide.

6. The electrolyte according to claim 4, characterized in that, The magnesium borate ester was prepared by reacting borate ester and magnesium salt; The borate esters include at least one of trimethyl borate, triethyl borate, triisopropyl borate, tri-n-butyl borate, tris(2,2,2-trifluoroethyl) borate, hexafluoroborate, tris(pentafluorophenyl)borane, pinacol borane, pinacol borate, catechol borane, catechol borate, 1,8-naphthyldiaminoborate, MIDA borate, diethanolamine borate, bis(neopentylethylene glycol) diborate, bis(pinacol) diborate, bis(catechol) diborate, or pinacol diborate. The magnesium salt was prepared by reacting a magnesium source with a nucleophile. The magnesium source includes at least one of magnesium dihydrogenate, alkyl magnesium salt, or carboxylated magnesium salt; the alkyl magnesium salt includes at least one of diethyl magnesium, di-n-butyl magnesium, di-sec-butyl magnesium, di-butyl(isopropyl) magnesium, di-n-butylethyl magnesium, or n-butyl-sec-butyl magnesium; the carboxylated magnesium salt includes at least one of magnesium formate, magnesium acetate, magnesium propionate, and / or magnesium formate. The nucleophile includes at least one of an alcohol, an acid, or an amine. The alcohol compounds include at least one of monohydric alcohols or polyhydric alcohols; the monohydric alcohols include ethanol, difluoroethanol, trifluoroethanol, 1-phenyl-2,2,2-trifluoroethanol, isopropanol, 1,3-dibromo-2-propanol, 2-phenylisopropanol, trifluoropropanol, trifluoroisopropanol, hexafluoroisopropanol, perfluorotert-butanol, 2-trifluoromethyl-2-propanol, 3-perfluorobutylpropanol, 1,1,1,3, At least one of 3,3-hexafluoro-2-phenyl-2-propanol, 2,2-bis(trifluoromethyl)propanol, tetrahydropyran-4-ol, or tetrahydrofuran-methanol; the polyol compound includes at least one of ethylene glycol, 2,3-butanediol, 2,3-diphenyl-2,3-butanediol, 2,3-dimethyl-2,3-butanediol, 1,2,4-butanetriol, or hexafluoro-2,3-bis(trifluoromethyl)-2,3-butanediol; The acid compounds include at least one of monocarboxylic acid compounds or polycarboxylic acid compounds; the monocarboxylic acid compounds include at least one of formic acid, acetic acid, propionic acid, 2,2-dimethylpropionic acid, benzoic acid, phenylacetic acid, 2-hydroxy-2-phenylacetic acid, trifluoroacetic acid, valeric acid, hexanoic acid, octanoic acid, p-toluenesulfonic acid, p-methoxybenzoic acid, trifluoromethanesulfonic acid, fluorosulfonic acid, hydrochloric acid, or hexafluorophosphate; the polycarboxylic acid compounds include oxalic acid and malonic acid. At least one of the following: succinic acid, glutaric acid, adipic acid, sebacic acid, maleic acid, trans-butenedioic acid, phthalic acid, isophthalic acid, terephthalic acid, 2,3-dihydroxysuccinic acid, 2-hydroxysuccinic acid, 2-hydroxypropane-1,2,3-tricarboxylic acid, isocitric acid, propene-1,2,3-tricarboxylic acid, pyromellitic acid, trimellitic acid, ethylenediaminetetraacetic acid, inositol hexaphosphate, sulfuric acid, phosphoric acid, carbonic acid, sulfurous acid, boric acid, or silicic acid; The amine compound preferably includes at least one of hexamethyldisilazane, hexaethyldisilazane, tris(trimethylsilyl)amine, N,N-bis(trimethylsilyl)methylamine, bis(trifluoromethanesulfonyl)imide, bis(fluorosulfonyl)imide, bis(pentafluoroethanesulfonyl)imide or bis(dimethylamino)tert-butylamine.

7. The electrolyte according to claim 1, characterized in that, The electrolyte also includes a solvent, which includes at least one of ether solvents or amine solvents.

8. The electrolyte according to claim 7, characterized in that, The ether solvent is at least one of a chain ether solvent or a cyclic ether solvent; the chain ether solvent includes at least one of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, or tetraethylene glycol dimethyl ether; the cyclic ether solvent includes at least one of tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, or 1,3-dioxolane; and / or The amine solvent includes at least one of chain alkoxyamine solvents or cyclic alkoxyamine solvents; the chain alkoxyamine solvent includes at least one of 2-methoxyethylamine, 2-ethoxyethylamine, 3-methoxypropylamine, 1-methoxy-2-propylamine, 2-(2-methoxyethoxy)ethylamine, N-(2-methoxyethyl)ethylamine, or 2-(dimethylamino)ethylmethyl ether; the cyclic alkoxyamine solvent includes at least one of 2-(2-methoxyethyl)morpholine, 4-methoxymethylpiperidine, N-(2-methoxyethyl)tetrahydropyrrole, 3-methoxyazacyclobutane, or 2-(methoxymethyl)tetrahydrofuran-3-amine.

9. A method for preparing an electrolyte, characterized in that, The method includes: The magnesium salt and the boride with BO bond are reacted first to obtain the magnesium boride; The magnesium boride and alkali metal salt are mixed to obtain an electrolyte, which is a magnesium-ion battery electrolyte. The boron element in the magnesium boride exists in the electrolyte in a tetracoordinate form.

10. The method for preparing the electrolyte according to claim 9, characterized in that, The method for preparing the magnesium salt includes: A second reaction is carried out between the magnesium source and the nucleophile to obtain the magnesium salt.

11. A single battery cell, characterized in that, The battery cell is a magnesium-ion battery, and the battery cell includes the electrolyte of any one of claims 1 to 8 or the electrolyte prepared by the method of any one of claims 9 to 10.

12. The battery cell according to claim 11, characterized in that, The battery cell includes a negative electrode sheet, at least a portion of the surface of which is covered with an SEI film. The SEI film is composed of alkali metal borides, which contain Mg and have BO bonds.

13. The battery cell according to claim 12, characterized in that, The alkali metal borides include Mg[B(OR4)4]2[M + ] or Mg[B(OR5) n (NR6) 4-n ]2[M + At least one of the following, wherein R4, R5 and R6 independently include at least one of ethyl, 2,2-difluoroethyl, 2,2,2-trifluoroethyl, 1-phenyl-2,2,2-trifluoroethyl, isopropyl, 1,3-dibromo-2-propyl, 1-phenylethyl, 3,3,3-trifluoropropyl, 1,1,1-trifluoro-2-propyl, hexafluoroisopropyl, perfluorotert-butyl, 2-trifluoromethyl-2-propyl, 3-perfluorobutylpropyl, 1,1,1,3,3,3-hexafluoro-2-phenyl-2-propyl, 2,2-bis(trifluoromethyl)propyl or tetrahydrofuranmethyl, and M includes an alkali metal element.

14. The battery cell according to any one of claims 11 to 13, characterized in that, The battery cell is a magnesium oxide battery, a magnesium sulfide battery, a magnesium sulfide battery, or a magnesium organic battery.

15. A secondary battery, characterized in that, The secondary battery comprises the battery cell according to any one of claims 11 to 14.

16. An electrical appliance, characterized in that, The electrical device includes a battery cell as described in any one of claims 11 to 14 or a secondary battery as described in claim 15.

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