An ultra-long-life and ultra-low overpotential wide-temperature-range magnesium battery electrolyte

Abstract

The application discloses a kind of super-long life and super-low overpotential wide temperature range magnesium battery electrolyte, for existing magnesium battery electrolyte desolvation kinetics slow, TFSI ‑ Easy to cause interface passivation, short cycle life and narrow working temperature range problems, using pyrazole nitrogen-containing heterocyclic cosolvent competitive coordination strategy realizes performance control.Pyrazole component is weakened by cation-π interaction Mg 2+ Strong coordination to reduce desolvation energy barrier, anchor TFSI ‑ Inhibit the formation of passivation layer, and in situ form C x N y Interface layer induces magnesium uniform deposition.The electrolyte described in the application is simple to prepare, has low polarization, long cycle and wide temperature characteristics, and can provide electrolyte solutions for high-performance magnesium batteries.

Description

Technical Field

[0001] This invention relates to the field of rechargeable magnesium battery technology, and specifically to a magnesium battery electrolyte with ultra-long lifespan and ultra-low overpotential and wide temperature range. Background Technology

[0002] Rechargeable magnesium metal batteries (RMBs) are considered strong candidates for next-generation energy storage systems due to their high volumetric capacity and excellent safety performance.

[0003] However, the practical application of rechargeable magnesium metal batteries is still severely limited by the electrolyte system. At the magnesium salt level, bis(trifluoromethanesulfonylimide)magnesium exhibits a wide electrochemical stability window due to the large ionic radius and highly delocalized negative charge distribution of its anion, but TFSI... - Anions readily undergo irreversible electrochemical decomposition on the surface of the magnesium anode, generating an ion-insulating passivation layer mainly composed of MgF2 and MgO. This passivation layer severely hinders the growth of Mg. 2+ Reversible deposition and dissolution at the electrode interface lead to low coulombic efficiency and rapid capacity decay during cycling. At the solvent level, amine solvents widely used in magnesium battery electrolytes are mainly divided into two systems: chain amines and cyclic amines. Chain amine solvents, such as 2-methoxyethylamine, dimethylamine, and isobutylamine, can effectively regulate Mg2+ by utilizing the strong Lewis basicity of nitrogen atoms. 2+ The solvated structure, but the nitrogen atom and Mg 2+ Excessive coordination between them leads to Mg 2+ The desolvation process faces an extremely high activation energy barrier, manifested as a high deposition overpotential and limited rate performance; cyclic amine solvents, such as imidazole compounds, although their sp... 2 While the electron-donating ability of hybrid nitrogen atoms participating in conjugated large π bonds is somewhat weakened, the electron-donating tendency of carbon atoms on the imidazole ring remains strong, making them prone to strong chemisorption or irreversible side reactions with the magnesium anode, resulting in insufficient interfacial stability. This also leads to problems in the overall performance of the electrolyte: existing magnesium battery electrolyte systems generally suffer from high deposition overpotential, short cycle life, and low deposition dissolution efficiency, and are difficult to maintain stable electrochemical performance over a wide temperature range, limiting the practical application of rechargeable magnesium metal batteries under extreme environmental conditions. In addition, existing strategies for improving electrolyte performance usually require the introduction of costly ionic liquid additives or complex ratio control of multiple additives, which not only increases the preparation cost and process complexity of the electrolyte, but also often brings negative effects such as increased electrolyte viscosity and decreased ionic conductivity, hindering large-scale commercialization. Summary of the Invention

[0004] To address the aforementioned shortcomings of existing technologies, this invention provides a magnesium battery electrolyte with ultra-long lifespan and ultra-low overpotential across a wide temperature range. Utilizing the characteristics of magnesium salts, a novel wide-temperature magnesium-based electrolyte is synthesized based on a co-solvent competitive coordination strategy. This electrolyte possesses advantages such as simple preparation process, low cost, high current tolerance, long cycle life, and high coulombic efficiency, thereby solving the problems of high overpotential, low deposition and dissolution efficiency, and short cycle life in existing electrolytes.

[0005] To achieve the above objectives, in a first aspect, the present invention provides an ultra-long lifespan and ultra-low overpotential wide-temperature range magnesium battery electrolyte, wherein the electrolyte is composed of a magnesium salt, a nitrogen-containing heterocyclic co-solvent, and an organic solvent; wherein the magnesium salt is bis(trifluoromethanesulfonylimide)magnesium; the nitrogen-containing heterocyclic co-solvent is any one of 1-methylpyrazole, 1-ethylpyrazole, 1-propylpyrazole, 1-methyl-3-trifluoromethyl-1H-pyrazole, 1-ethyl-3-trifluoromethyl-1H-pyrazole, and 1-propyl-3-trifluoromethyl-1H-pyrazole; the organic solvent is any one of 3-methoxypropylamine, 2-methoxyethylamine, 3-methoxyisopropylamine, 1-methoxypropyldiamine, 3-isopropoxypropylamine, ethylene glycol dimethyl ether, or tetrahydrofuran; and the concentration of the magnesium salt in the organic solvent is 0.1 mol / L to 0.4 mol / L. The volume ratio of nitrogen-containing heterocyclic cosolvent to organic solvent is (1:19) to (1:10).

[0006] Preferably, the electrolyte is prepared by the following steps:

[0007] Step 1: Dissolve the magnesium salt in an organic solvent and mix thoroughly at 20℃~25℃ to obtain a mixed solution;

[0008] Step 2: Add a nitrogen-containing heterocyclic cosolvent to the mixed solution obtained in Step 1, and stir to obtain the electrolyte.

[0009] Preferably, both steps 1 and 2 are performed in an inert gas atmosphere.

[0010] Preferably, in the mixing system of step 1 and step 2, the water content and oxygen content are both less than 0.01 ppm.

[0011] Preferably, the magnesium salt is pretreated as follows:

[0012] The magnesium salt was vacuum dried at 70℃~90℃ for at least 24 hours and then sealed for storage.

[0013] Preferably, the organic solvent is pretreated as follows:

[0014] The molecular sieve is heated to 300℃~400℃ and activated for 4~6 hours, then added to the organic solvent and sealed for storage.

[0015] Preferably, under normal temperature conditions, the Mg||Mg symmetric cell operates at 0.1 mA / cm². 2 Under current density conditions, it can cycle stably for more than 4,500 hours; under extreme temperature scenarios, the Mg||Mg symmetric battery can cycle stably for 700 hours in a low temperature environment of -10℃ and for 180 hours in a high temperature environment of 80℃; under full-cell high-rate scenarios, the Mg||Mo6S8 full cell can cycle stably for 9,000 times at a high current density of 3C, and the discharge specific capacity after cycling is still maintained at 75~80 mAh / g.

[0016] Secondly, the present invention provides a rechargeable magnesium battery, wherein the electrolyte in the rechargeable magnesium battery is the aforementioned magnesium battery electrolyte with ultra-long lifespan and ultra-low overpotential and wide temperature range.

[0017] Preferably, the rechargeable magnesium battery is capable of stable cyclic operation in a wide temperature range of -10℃ to 80℃.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. This invention discovers that by introducing a pyrazole-based nitrogen-containing heterocyclic cosolvent, the delocalized π electron cloud in the pyrazole molecule can be utilized in conjunction with Mg... 2+ The weak cation-π interaction between them competitively weakens Mg. 2+ Strong coordination bonds between Mg and organic solvent molecules 2+ The solvated sheath layer changes from a strong coordination mode to a weak coordination mode, thereby significantly reducing Mg 2+ The desolvation activation barrier at the electrode interface reduces the deposition overpotential to below 46 mV, solving the problem of nitrogen atoms reacting with Mg atoms in existing chain amine solvent systems. 2+ Technical problems such as sluggish desolvation kinetics and high deposition overpotential caused by excessive coordination; and the use of pyrazole co-solvents for TFSI. - An anchoring effect occurs, reducing TFSI - The free concentration in the solvated outer layer of the sheath was reduced, thereby suppressing TFSI. - The irreversible electrochemical decomposition at the magnesium anode interface and the resulting formation of an ion-insulating passivation layer solve the problem of TFSI in the bis(trifluoromethanesulfonylimide) magnesium system. - Anions readily form a passivation film mainly composed of MgF2 and MgO on the surface of the magnesium anode, thereby hindering the formation of Mg. 2+ Technical issues related to reversible deposition and dissolution.

[0020] 2. This invention also discovered that the lower LUMO energy level of pyrazole cosolvents allows them to preferentially undergo electrochemical decomposition at the electrode interface compared to organic solvents, resulting in the in-situ generation of alternating organic and inorganic compounds rich in C on the magnesium anode surface.x N y The solid electrolyte interface layer of the component forms a dense protective film on the surface of the magnesium anode through physical adsorption, effectively isolating the electrolyte from direct contact with the active metal magnesium. This solves the technical problem of irreversible loss of active material due to continuous side reactions between the electrolyte and the magnesium anode. Furthermore, this invention discovers that the preferential adsorption characteristics of pyrazole co-solvents on the magnesium anode surface generate an electrostatic shielding effect, guiding the Mg... 2+ The uniform distribution and deposition on the electrode surface inhibits the nucleation and growth of magnesium dendrites from the source, solving the technical problem of dendrite growth caused by local current density concentration on the magnesium anode surface, which leads to battery short circuit failure.

[0021] 3. Regarding the limitation of component ratios, this invention ensures that the electrolyte maintains sufficient ionic conductivity at low temperatures without a sharp increase in battery internal resistance due to insufficient ion transport capacity by controlling the magnesium salt concentration within the range of 0.1 mol / L to 0.4 mol / L. Simultaneously, it prevents a decrease in ion transport number and an increase in transport resistance due to excessively high ion concentration at high temperatures. Furthermore, by controlling the volume ratio of the nitrogen-containing heterocyclic co-solvent to the organic solvent within the range of 1:19 to 1:10, this ensures that the co-solvent occupies a sufficient coordination fraction in the solvated structure to achieve the desired effect on TFSI. - Effective anchoring and Mg 2+ The effective control of the solvation structure, without introducing new desolvation resistance due to an excessively high proportion of cosolvent, solves the technical problem of existing electrolyte systems struggling to maintain stable electrochemical performance across a wide temperature range through the synergistic effect of the aforementioned concentrations and ratios. At the preparation process level, this invention employs a two-step, one-pot method—dissolving magnesium salts in an organic solvent and then adding a nitrogen-containing heterocyclic cosolvent—to prepare the electrolyte at room temperature. This eliminates the need for costly ionic liquid additives or complex ratio control of multiple additives, thus addressing the technical problems of existing strategies for improving electrolyte performance, such as high preparation costs, complex processes, and often accompanied by increased electrolyte viscosity and decreased ionic conductivity.

[0022] 4. This invention further discovers that the reduction of the desolvation energy barrier is related to TFSI. - The suppression of the passivation layer constitutes a positive coupling during the interfacial charge transfer process: the reduction of the desolvation energy barrier allows Mg to... 2+ It can reach the electrode surface more quickly to complete charge transfer, while TFSI - The elimination of the passivation layer ensures that the electrode surface always has sufficient electrochemical active sites for Mg. 2+ Deposition, along with the combined effect of these two factors, prevents significant degradation of the interfacial charge transfer impedance during long-term cycling, thereby enabling Mg||Mg symmetric cells at 0.1 mA / cm².2 Stable cycling for 4500 hours at current density fundamentally solves the technical problems of short cycle life and low deposition dissolution efficiency of existing magnesium battery electrolytes. Stable C x N y Another synergistic relationship is formed between the interface layer and the improvement of desolvation kinetics: C x N y The compound with ionic conductivity in the interface layer is Mg. 2+ It provides a continuous transmission channel, ensuring the quality of Mg. 2+ The rapid supply at the interface is not hindered by the presence of the interface layer, while the reduction of the desolvation energy barrier ensures the supply of Mg. 2+ After crossing the interface layer, it can rapidly undergo desolvation and deposition as metallic magnesium. Both processes work together to maintain the steady-state operation of the interfacial electrochemical process at high current densities, allowing the electrolyte to operate at 5 mA / cm². 2 It can still operate normally under high current density, solving the technical problems of intensified interface polarization and rapid capacity decay under high-rate conditions. The uniform deposition characteristics achieved by the electrostatic shielding effect of pyrazole co-solvents are similar to those of C. x N y The mechanical protective functions of the interface layers complement each other at the structural level: uniform deposition avoids mechanical damage to the SEI layer caused by localized tip deposition, while the intact SEI layer prevents the exposure of fresh magnesium surfaces and their continuous side reactions with the electrolyte. These two aspects mutually maintain and reinforce each other, avoiding the vicious cycle of "dendrite growth—SEI layer rupture—exacerbated side reactions—interface deterioration," further consolidating long-term cycling stability. In terms of temperature adaptability, the synergistic constraint of magnesium salt concentration and co-solvent ratio, along with the regulation of solvation structure, forms a functional synergy: reasonable concentrations and ratios ensure that the solvation structure does not undergo drastic recombination or dissociation during temperature changes, allowing Mg... 2+ The solvation-desolventization equilibrium can be maintained in a state favorable to rapid charge transfer over a wide temperature range, while C x N y The interface layer maintains its structural integrity under temperature fluctuations, and together they ensure that the electrolyte can maintain stable electrochemical performance in a wide temperature range of -10℃ to 80℃, solving the technical problems of narrow operating temperature range and rapid performance degradation of existing electrolyte systems under extreme temperatures. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a cycle number-coulomb efficiency diagram for the Mg||Mg symmetric battery of Example 1 and the comparative example of the present invention.

[0025] Figure 2 Linear scanning voltammetry diagrams of the electrolyte prepared in Example 1 of this invention on different working electrodes.

[0026] Figure 3 This is a graph showing the long-cycle performance of a Mg||Mg symmetric battery with the electrolyte prepared in Example 1 of this invention.

[0027] Figure 4 The graph shows the cycling performance of the Mg||Mg symmetric battery with the electrolyte prepared in Example 1 of this invention at a low temperature of -10℃.

[0028] Figure 5 The graph shows the cycling performance of the Mg||Mg symmetric battery with the electrolyte prepared in Example 1 of this invention at a high temperature of 80°C.

[0029] Figure 6 The graph shows the long-cycle performance of the Mg||Mo6S8 full cell with electrolyte prepared in Example 1 of this invention under high current at 3C. Detailed Implementation

[0030] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments and accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on this invention are within the scope of protection of this invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Reagents or instruments whose manufacturers are not specified can be obtained commercially.

[0031] Unless otherwise specified in the specific context, the numerical ranges listed herein include upper and lower limits, as well as all integers and fractions within those ranges, and are not limited to the specific values ​​listed when defining the range. For numerical ranges, endpoint values ​​of various ranges, endpoint values ​​of various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. The term "and / or" used herein is inclusive; for example, "A and / or B" means only A, or only B, or both A and B. Terms such as "about," "substantially the same," and similar expressions used herein indicate that reasonable deviations are permissible.

[0032] I. A magnesium battery electrolyte with ultra-long lifespan and ultra-low overpotential over a wide temperature range

[0033] The core technical problems addressed by this invention include three aspects: First, TFSI in the bis(trifluoromethanesulfonylimide) magnesium system. - Anions readily undergo irreversible decomposition on the surface of the magnesium anode, forming an ion-insulating passivation film that hinders the growth of magnesium. 2+ The reversible deposition and dissolution of amines lead to low coulombic efficiency and reduced cycle life; secondly, the nitrogen atoms and Mg atoms in existing amine solvent systems are... 2+ The coordination between them is too strong, leading to Mg 2+ The desolvation process is kineticly slow, resulting in high deposition overpotential and limited rate performance; thirdly, existing electrolyte systems are difficult to maintain stable electrochemical performance over a wide temperature range.

[0034] To address the first problem mentioned above, this invention, from the perspective of solvation structure regulation, discovers that introducing pyrazole-based nitrogen-containing heterocyclic compounds as co-solvents into the electrolyte system utilizes pyrazole molecules to catalyze TFSI. - Anchored within the solvated sheath, its free concentration and decomposition probability at the electrode interface can be reduced. Regarding the second problem mentioned above, this invention discovers the use of the delocalized π-electron cloud in the pyrazole molecule and Mg... 2+ The weak cation-π interaction between them partially substitutes Mg through competitive coordination. 2+ Strong coordination bonds between Mg and organic solvent molecules 2+ The solvated sheath transforms from a strong coordination mode to a weak coordination mode, thereby lowering the desolvation activation barrier. Addressing the third issue mentioned above, as well as the interfacial stability problem, this invention discovers that the lower LUMO energy level of pyrazole cosolvents allows them to preferentially undergo electrochemical decomposition at the electrode interface compared to organic solvents, thus enabling the in-situ construction of C-rich... x N y The solid electrolyte interface layer of the components was also found to have a preferential adsorption characteristic of pyrazole molecules on the magnesium anode surface, which can achieve an electrostatic shielding effect to guide the Mg... 2+Uniform deposition. Therefore, this invention provides an ultra-long lifespan and ultra-low overpotential wide-temperature range magnesium battery electrolyte, wherein the electrolyte is composed of a magnesium salt, a nitrogen-containing heterocyclic co-solvent, and an organic solvent; wherein the magnesium salt is bis(trifluoromethanesulfonylimide)magnesium; the nitrogen-containing heterocyclic co-solvent is any one of 1-methylpyrazole, 1-ethylpyrazole, 1-propylpyrazole, 1-methyl-3-trifluoromethyl-1H-pyrazole, 1-ethyl-3-trifluoromethyl-1H-pyrazole, and 1-propyl-3-trifluoromethyl-1H-pyrazole; the organic solvent is any one of 3-methoxypropylamine, 2-methoxyethylamine, 3-methoxyisopropylamine, 1-methoxypropyldiamine, 3-isopropoxypropylamine, ethylene glycol dimethyl ether, or tetrahydrofuran; in the organic solvent, the concentration of the magnesium salt is 0.1 mol / L to 0.4 mol / L, and the volume ratio of the nitrogen-containing heterocyclic co-solvent to the organic solvent is (1:19) to (1:10).

[0035] In some embodiments of the present invention, the magnesium salt is bis(trifluoromethanesulfonylimide) magnesium. The core consideration for selecting Mg(TFSI)2 in the present invention lies in TFSI. - The large ionic radius and highly delocalized negative charge distribution of the anions give Mg(TFSI)2-based electrolytes a wide electrochemical stability window, enabling them to be compatible with various high-voltage cathode material systems. This is a fundamental performance requirement that other magnesium salts in the current technology cannot simultaneously meet. However, the Mg(TFSI)2 system has an inherent interfacial defect, namely, TFSI... - Anions readily undergo irreversible electrochemical decomposition on the surface of the magnesium anode, generating an ion-insulating passivation layer mainly composed of MgF2 and MgO, which severely hinders the growth of magnesium. 2+ Reversible deposition and dissolution of TFSI. This invention introduces a pyrazole-based nitrogen-containing heterocyclic co-solvent to achieve this. - Anchored within the solvated sheath, this reduces the free concentration and decomposition probability of Mg(TFSI)2 at the electrode interface, thus overcoming its inherent passivation defects while retaining the advantage of a wide electrochemical window. This design approach eliminates the need for costly ionic liquid additives or complex ratio adjustments of multiple additives to improve interfacial stability, as is required in existing technologies. A wide electrochemical window and good interfacial compatibility can be achieved simply by introducing a single co-solvent.

[0036] In some embodiments of the present invention, the nitrogen-containing heterocyclic co-solvent is any one of 1-methylpyrazole, 1-ethylpyrazole, 1-propylpyrazole, 1-methyl-3-trifluoromethyl-1H-pyrazole, 1-ethyl-3-trifluoromethyl-1H-pyrazole, and 1-propyl-3-trifluoromethyl-1H-pyrazole. In the solvation structure control strategy of magnesium battery electrolytes, the choice of co-solvent or additive directly determines the Mg... 2+The coordination mode of the solvated sheath, the composition and structure of the interfacial SEI layer, and the overall electrochemical stability of the electrolyte are all important factors. Existing nitrogen-containing compounds used to improve the performance of magnesium battery electrolytes mainly fall into two categories: chain amines and cyclic amines. Chain amine solvents, such as 2-methoxypropylamine, dimethylamine, and isobutylamine, can effectively penetrate the Mg... 2+ The first solvation layer modulates the solvation structure, but nitrogen atoms and Mg 2+ Excessive coordination between them leads to Mg 2+ The desolvation process faces an extremely high activation energy barrier, resulting in high deposition overpotentials and limited rate performance. Furthermore, strong coordination makes the solvated sheath prone to drastic structural reorganization with temperature changes, which is detrimental to wide-temperature applications. Among cyclic amine solvents, imidazole compounds are the most widely studied representatives, and their sp... 2 The lone pair of electrons in the hybrid nitrogen atom participates in the conjugated large π bond, which weakens its electron-donating ability, and its interaction with Mg... 2+ The coordination strength of imidazole compounds is lower than that of chain amines, but the electron-donating tendency of the carbon atom on the imidazole ring is still relatively strong. This makes them prone to strong chemisorption or irreversible side reactions with the magnesium anode, resulting in insufficient interfacial stability and difficulty in forming a stable protective interfacial layer on the electrode surface. Although pyridine compounds also belong to nitrogen-containing heterocyclic systems, their molecules contain only one nitrogen atom, lacking the additional coordination site and electronic structure regulation space provided by a second nitrogen atom, making it difficult to simultaneously achieve coordination with Mg... 2+ Regulation of solvation structure and TFSI - Effective anchoring of anions. In pyrrole compounds, the lone pair electrons of the nitrogen atom are fully involved in the aromatic conjugated system, resulting in extremely weak coordination ability as a Lewis base, making it difficult to effectively enter Mg. 2+ The solvation sheath plays a regulatory role. This invention selects pyrazole-based nitrogen-containing heterocyclic compounds as co-solvents because it has discovered that pyrazole molecules possess unique electronic structures and coordination chemistry characteristics: Firstly, the presence of two adjacent nitrogen atoms in the pyrazole ring results in a fundamental difference in the distribution and polarization of the π-electron cloud on the ring compared to mono- or di-nitrogen heterocycles such as imidazole and pyridine. The delocalized π-electron cloud of the pyrazole molecule interacts with Mg... 2+ A weak cation-π interaction can occur between them, the strength of which lies between the strong coordination of chain amines and the extremely weak coordination of pyrrole, allowing for competitive partial substitution of Mg. 2+ The strong coordination bonds with organic solvent molecules transform the solvation sheath from a strong coordination mode to a weak coordination mode, effectively lowering the desolvation activation barrier without losing the ability to regulate the solvation structure due to excessively weak coordination. Secondly, the cooperative electronic effect of the two nitrogen atoms in the pyrazole molecule enables it to bind to TFSI. - It produces an effective anchoring effect, a characteristic not possessed by chain amines and imidazole compounds. Chain amines preferentially occupy Mg due to their excessively strong coordination.2+ The coordination sites of pyrazoles are limited, making it difficult to simultaneously regulate anions. Imidazoles, due to the strong electron-donating tendency of carbon atoms, tend to undergo side reactions with magnesium anodes rather than forming stable solvated structures with anions. Thirdly, pyrazole compounds have a low LUMO energy level, allowing them to preferentially undergo electrochemical decomposition at the electrode interface compared to organic solvents, generating C-rich compounds in situ. x N y The solid electrolyte interface layer of the components possesses both ionic conductivity and chemical stability, while imidazole compounds struggle to form a continuous and dense protective interface layer during electrochemical decomposition. Fourth, pyrazole molecules exhibit preferential adsorption characteristics on the magnesium anode surface, and can guide Mg through electrostatic shielding effects. 2+ The uniform deposition of pyrazole-based nitrogen-containing heterocyclic compounds is reversible and stable, unlike imidazole compounds which consume active materials or damage interfacial structures due to strong adsorption. In summary, this invention reveals that pyrazole-based nitrogen-containing heterocyclic compounds exhibit comprehensive advantages over commonly used nitrogen-containing compounds in the prior art in four dimensions: coordination strength, anion anchoring ability, interfacial decomposition product characteristics, and surface adsorption behavior. These advantages make them an irreplaceable co-solvent choice in the solvation structure regulation strategy of this invention.

[0037] In some embodiments of the present invention, the organic solvent is any one of 3-methoxypropylamine, 2-methoxyethylamine, 3-methoxyisopropylamine, 1-methoxypropyldiamine, 3-isopropoxypropylamine, ethylene glycol dimethyl ether, or tetrahydrofuran. The present invention selects methoxyamine compounds and / or ether compounds as organic solvents. Based on the selection of magnesium salts and nitrogen-containing heterocyclic cosolvents, the present invention further discovers that there are differences in the compatibility of various organic solvents with the aforementioned two in the prior art. Methoxyamine compounds possess both ether bonds and amino groups as functional groups, and the oxygen atom in the ether bond provides moderate strength Mg... 2+ Coordination ability, ensuring Mg 2+ Effective solvation and ion transport are achieved through the amino group nitrogen atom, which provides additional coordination sites, contributing to the stability of the solvated structure. Compared to pure chain amine solvents, the introduction of ether bonds in methoxyamine compounds dilutes the coordination density of the amino group, avoiding the desolvation difficulties caused by excessive coordination. Compared to pure ether solvents, the introduction of amino groups in methoxyamine compounds enhances the solvent molecule's affinity for Mg. 2+ The coordination ability of these compounds improves the solubility of magnesium salts and the ionic conductivity of the electrolyte. Ether compounds such as ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetrahydrofuran, and 2-methyltetrahydrofuran, as components of the organic solvent, provide stable magnesium... 2+It possesses a coordination environment and excellent ion transport channels, and its electrochemical reduction stability is superior to ester solvents, preventing the formation of a thick passivation layer on the magnesium anode surface. This invention utilizes methoxyamine compounds and / or ether compounds in combination with pyrazole-based nitrogen-containing heterocyclic co-solvents to address the oxidation of Mg... 2+ Weak coordination regulation of solvation structure and its effect on TFSI - The anchoring effect of anions compensates for the shortcomings of organic solvents in terms of interfacial stability and solvation structure optimization, enabling the electrolyte to achieve comprehensive performance goals such as wide electrochemical window, low deposition overpotential, high coulombic efficiency and wide temperature range stability without the need to introduce high-cost ionic liquids or complex additive systems.

[0038] In some embodiments of the present invention, the concentration of magnesium salt in the organic solvent is 0.1 mol / L to 0.4 mol / L, and the volume ratio of the nitrogen-containing heterocyclic cosolvent to the organic solvent is (1:19) to (1:10). If the magnesium salt concentration is higher than this range, it will lead to a decrease in the transport number of ions in the electrolyte, increasing the ion transport resistance. Conversely, if the concentration is lower than this range, it will lead to low ionic conductivity and poor ion transport capacity, resulting in a significant increase in the internal resistance of the battery. Therefore, the concentration of magnesium salt in the organic solvent can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, or 0.4 mol / L, or any range and sub-range between any two of the above specific values. A concentration higher than this range will prevent effective competitive coordination, making desolvation difficult and leading to a decrease in the stability of the magnesium battery. A concentration lower than this range will prevent effective suppression of TFSI. - The passivation is achieved. Therefore, the volume ratio of the nitrogen-containing heterocyclic cosolvent to the organic solvent can be 1:19, 2:18, 3:17, 4:16, 5:15, 6:14, 7:13, 8:12, 9:11, or 10:10, or any range and sub-range between any two of the above specific values; it should be understood that in specific embodiments, any of the above ranges can be combined with any other ranges to achieve the technical effects described in this invention.

[0039] In some embodiments of the present invention, the electrolyte is prepared by the following steps:

[0040] Step 1: Dissolve the magnesium salt in an organic solvent and mix thoroughly at 20℃~25℃ to obtain a mixed solution;

[0041] Step 2: Add a nitrogen-containing heterocyclic cosolvent to the mixed solution obtained in Step 1, and stir to obtain the electrolyte.

[0042] In some embodiments of the present invention, steps 1 and 2 are both performed under an inert gas atmosphere. Under the protection of an inert gas atmosphere, oxygen can be prevented from entering the electrolyte, thereby protecting the magnesium anode from oxidation and also protecting the stability of the electrolyte.

[0043] In some embodiments of the present invention, in the mixing system of step 1 and step 2, the water content and oxygen content are both less than 0.01 ppm, thereby eliminating the side reactions of water and oxygen in the system and reducing the generation of by-products.

[0044] In some embodiments of the present invention, the magnesium salt is pretreated as follows:

[0045] The magnesium salt is vacuum dried at 70℃~90℃ for at least 24 hours and then sealed for storage to remove water and oxygen from the magnesium salt.

[0046] In some embodiments of the present invention, the organic solvent is pretreated as follows:

[0047] The molecular sieve is heated to 300℃~400℃ and activated for 4~6 hours, then added to the organic solvent, and then sealed and stored to remove water and oxygen from the solvent.

[0048] II. A rechargeable magnesium battery

[0049] The electrolyte in the rechargeable magnesium battery of the present invention is the aforementioned ultra-long lifespan and ultra-low overpotential wide-temperature-range magnesium battery electrolyte. Specifically, the rechargeable magnesium battery can stably cycle and operate in a wide temperature range of -10℃ to 80℃.

[0050] III. Examples and Comparative Examples

[0051] Example 1

[0052] Step 1: Solvent pretreatment: Add 3Å molecular sieves that have been activated at 300℃ for 5 hours to the organic solvent 3-methoxypropylamine while hot, and store in a glove box in a sealed container.

[0053] Step 2: Pretreatment of magnesium salt electrolyte: After being vacuum dried at 80°C for 24 hours, bis(trifluoromethanesulfonylimide) magnesium is placed in a glove box and sealed for storage.

[0054] Step 3: Preparation of the electrolyte: All reactions were carried out under an anhydrous and oxygen-free inert atmosphere. Take 1.125 ml of 3-methoxypropylamine, slowly add 0.2192 g of magnesium bis(trifluoromethanesulfonylimide), and stir for 10 min; then add 125 μl of 1-methyl-3-trifluoromethyl-1H-pyrazole while stirring, and stir for 24 hours to obtain the electrolyte.

[0055] Example 2

[0056] This example is an improvement on Example 1, except that the nitrogen-containing heterocyclic cosolvent is 1-methylpyrazole, and the concentration of bis(trifluoromethanesulfonylimide) magnesium in the solvent is 0.3 mol / L. All other steps are exactly the same as in Example 1.

[0057] Example 3

[0058] This is an improvement on Example 1, except that the nitrogen-containing heterocyclic cosolvent is 1-ethylpyrazole, and the concentration of bis(trifluoromethanesulfonylimide) magnesium in the solvent is 0.3 mol / L. All other steps are exactly the same as in Example 1.

[0059] Example 4

[0060] This is an improvement on Example 1, except that the nitrogen-containing heterocyclic cosolvent is 1-propylpyrazole, and the concentration of bis(trifluoromethanesulfonylimide) magnesium in the solvent is 0.3 mol / L. All other steps are exactly the same as in Example 1.

[0061] Example 5

[0062] The improvement upon Example 1 is as follows: the nitrogen-containing heterocyclic co-solvent is 125 μl of 1-ethyl-3-trifluoromethyl-1H-pyrazole, and the concentration of bis(trifluoromethanesulfonylimide)magnesium in the solvent is 0.3 mol / L. All other steps are exactly the same as in Example 1.

[0063] Example 6

[0064] This is an improvement on Example 1, except that the concentration of bis(trifluoromethanesulfonyl)magnesium in the organic solvent is 0.2 mol / L. All other steps are exactly the same as in Example 1.

[0065] Example 7

[0066] This is an improvement on Example 1, except that the concentration of magnesium bis(trifluoromethanesulfonylimide) in the organic solvent is 0.4 mol / L. All other steps are exactly the same as in Example 1.

[0067] Comparative Example 1

[0068] This is an improvement on Example 1, except that the concentration of bis(trifluoromethanesulfonyl)magnesium in the organic solvent is 0.5 mol / L. All other steps are exactly the same as in Example 1.

[0069] Comparative Example 2

[0070] This is an improvement on Example 1, except that the concentration of bis(trifluoromethanesulfonyl)magnesium in the organic solvent is 0.6 mol / L. All other steps are exactly the same as in Example 1.

[0071] Comparative Example 3

[0072] This is an improvement on Example 1, except that the co-solvent is ethylamide. All other steps are exactly the same as in Example 1.

[0073] Comparative Example 4

[0074] This is an improvement on Example 1, except that the co-solvent is 2,2,2-trifluoroethyltrifluoromethane sulfonate. All other steps are exactly the same as in Example 1.

[0075] IV. Performance Testing

[0076] (1) Coulombic efficiency test of magnesium reversible deposition / dissolution performance

[0077] The reversible deposition / dissolution performance of the electrolyte was tested using a constant current charge-discharge (CP) method. Testing was conducted by assembling Mg||Mg symmetric CR2032 coin cells, with a magnesium metal sheet as both the positive and negative electrodes, a glass fiber membrane (GF / A) separator, and a current density of 0.5 mA / cm². 2 .

[0078] Taking Examples 1-4 as examples, the results obtained by comparing them with those of the comparative examples using the above test methods are as follows:

[0079] Examples 1-4: Electrolyte at 0.5 mA / cm 2 It was cycled 600 times at a current density. The deposition overpotential was 51 mV.

[0080] The relevant electrochemical performance of the comparative examples and Example 1 is shown in the table below. The electrolytes of Comparative Examples 1-4 at 0.1 mA / cm²... 2 The average deposition overpotential after 600 cycles at the specified current density was greater than that in Example 1, and the cycling stability was poor, indicating that the electrolytes of Comparative Examples 1-4 may still have TFSI. - The passivation and desolvation processes are difficult. However, the electrolytes in Examples 1-4 operate at 0.5 mA / cm². 2 At current densities, the cycle life exceeds 600 cycles, while the average deposition overpotential is only 51mV, and the cycle stability is good.

[0081] Table 1

[0082] Example 1 >600 h 51 mV Example 2 >600 h 66 mV Example 3 >600 h 60 mV Example 4 >600 h 65 mV Comparative Example 1 >600 h 94 mV Comparative Example 2 160 h 120 mV Comparative Example 3 420 h 133 mV Comparative Example 4 50 h 167 mV

[0083] from Figure 1It can be seen that as the magnesium salt concentration gradually increases from 0.2 mol / L to 0.6 mol / L, the deposition / dissolution overpotential of the battery exhibits a monotonically increasing trend. The overpotential of the 0.3 mol / L system is 51 mV, at the same level as the 52 mV of the 0.2 mol / L system. When the concentration increases to 0.4 mol / L, the overpotential gradually climbs, reaching 94 mV and 120 mV for the 0.5 mol / L and 0.6 mol / L systems, respectively. Furthermore, the voltage fluctuation amplitude of the high concentration groups increases significantly, and polarization continues to intensify during cycling. This result reflects an optimal matching range for the regulatory effect of magnesium salt concentration and pyrazole co-solvent: at a concentration of 0.3 mol / L, pyrazole molecules weaken the effect of Mg through cation-π interactions. 2+ Strong coordination bonding with amine solvents, and simultaneously with TFSI - Anions exert an anchoring effect to suppress interfacial decomposition. The reduction of the desolvation energy barrier and the suppression of the passivation layer work synergistically to achieve low overpotential and stable interfacial cycling. However, when the concentration exceeds 0.4 mol / L, enhanced ion association leads to solvation structure reorganization. The regulatory effect of the cosolvent is offset by the ion migration resistance brought about by the high concentration, while free TFSI... - The increase in the proportion of passivation layer leads to its continuous growth, which ultimately manifests as a sharp increase in overpotential and deterioration in cycling stability. This set of concentration gradient experiments verified the rationality of the concentration range of 0.1~0.4 mol / L, solving the technical problem that concentration optimization in traditional magnesium electrolyte systems cannot simultaneously take into account ionic conductivity and interfacial stability, and laying the concentration foundation for subsequent wide-temperature and long-cycle performance.

[0084] (2) Stability test of magnesium deposition / dissolution oxidation

[0085] The coulombic efficiency and oxidative stability of the electrolyte prepared in Example 1 for reversible magnesium deposition / dissolution were tested using linear voltammetry (LSV). The tests were conducted using assembled CR2032 coin cells, with a stainless steel (SS) positive electrode current collector, a magnesium sheet negative electrode, and a glass fiber membrane separator. The LSV voltage range was from open-circuit voltage to 5.0 V, and the scan rate was 25 mV / s.

[0086] The electrochemically stable potentials of the electrolyte prepared in Example 1 on molybdenum foil (Mo), aluminum foil (Al), and carbon-aluminum foil (C / Al) were 3.12 V, 3.29 V, and 3.30 V, respectively. The results are as follows: Figure 2 As shown, Figure 2 Linear scan voltammetry plots of the electrolyte prepared in Example 1 on different working electrodes were obtained. The scan rate was 5 mV / s, and the potential was expressed as Mg. 2+ / Mg is the reference. Figure 2As can be seen, it exhibits a wide electrochemical stability window across various current collector materials. This level of oxidative stability is closely related to the regulation of the solvation structure by pyrazole co-solvents in the electrolyte: the nitrogen-containing heterocyclic co-solvent alters the Mg... 2+ The solvated sheath composition reduces the coordination ratio of organic solvent molecules in the solvated structure, thus delaying the oxidative decomposition of the organic solvent at high potentials. Simultaneously, the lower LUMO energy level of the pyrazole cosolvent allows it to preferentially undergo electrochemical decomposition at the electrode interface compared to the organic solvent, generating C-rich compounds in situ on the negative electrode surface. x N y The solid electrolyte interface layer, composed of alternating organic and inorganic components, forms a dense protective film on the electrode surface through chemical bonding or physical adsorption. This effectively isolates the electrolyte from direct contact with the reactive magnesium metal, thus broadening the practically usable electrochemical window of the electrolyte from another perspective. The improved oxidative stability and the formation of the interface protective layer create a functional complementarity: the wide electrochemical window ensures that the electrolyte does not undergo bulk decomposition under high-potential conditions, while the stable C... x N y The interface layer prevents the electrolyte from being continuously consumed by side reactions on the negative electrode side. Together, they ensure that the electrolyte has sufficient electrochemical stability at both the positive and negative electrodes, providing a basic condition for matching different positive electrode materials and current collectors in the full battery system.

[0087] (3) Magnesium reversible deposition / dissolution performance test

[0088] The reversible deposition / dissolution performance and coulombic efficiency of the electrolyte prepared in Example 1 were tested using a constant current charge-discharge (CP) test. The test was conducted using an assembled CR2032 coin cell, with magnesium sheets as the positive and negative electrodes and a glass fiber membrane (GF / A) as the separator. The CP test was performed at a charge-discharge time of 30 min and a current density of 0.1 mA / cm². 2 ~1 mA / cm 2 .

[0089] The electrolyte prepared in Example 1, when used in practical applications at a current density of 0.1 mA / cm², 2 Under these conditions, the Mg||Mg battery can cycle stably for 4500 hours with a low deposition overpotential of 24 mV. Furthermore, no significant polarization growth or short-circuit signal was observed in the voltage curve during cycling. This demonstrates that uniform deposition avoids the mechanical damage to the SEI layer caused by localized tip deposition, ensuring the integrity of the C1 layer. x N y The interface layer prevents the exposure of fresh magnesium surfaces and their continued side reactions with the electrolyte, while the continuous improvement in desolvation kinetics ensures the protection of Mg. 2+After crossing the interface layer, it can rapidly complete desolvation and deposit as metallic magnesium. The three processes mutually maintain each other, avoiding the vicious cycle of dendrite growth—SEI layer rupture—aggravated side reactions—interface deterioration. This multi-level synergistic protection mechanism enables the interfacial electrochemical process to maintain a steady state during long-term operation, ultimately achieving a balance between an ultra-long cycle life of 4500 hours and high coulombic efficiency.

[0090] The electrolyte prepared in Example 1, when used in practical applications, exhibits performance at 0.1 mA / cm². 2 It can operate stably in a cyclic manner under current density conditions and in a wide temperature range of -10℃ to 80℃. Figure 4 and Figure 5 As shown, at 0.1 mA / cm 2 Under current density conditions, the battery maintained a stable voltage curve and low deposition / dissolution overpotential at low temperatures, without exhibiting a sharp increase in polarization or cycle interruption due to sudden temperature drops. Simultaneously, at high temperatures, the battery also demonstrated stable cycling behavior and controllable deposition / dissolution overpotential, without rapid performance degradation or thermal runaway caused by accelerated side reactions at high temperatures. This wide-temperature-range adaptability is primarily attributed to the synergistic control of magnesium salt concentration and co-solvent ratio in the electrolyte system. The magnesium salt concentration was controlled within the range of 0.1–0.4 mol / L, ensuring sufficient ionic conductivity at low temperatures to prevent a sharp increase in battery internal resistance due to insufficient ion transport capacity, while preventing a decrease in ion transport number and an increase in transport resistance due to excessively high ion concentration at high temperatures. The volume ratio of the nitrogen-containing heterocyclic co-solvent to the organic solvent was controlled between 1:19 and 1:10, ensuring that the co-solvent occupies an appropriate coordination share in the solvation structure, thus achieving the desired balance between magnesium and organic solvents. 2+ Effective regulation of solvation structure and control of TFSI - Effective anchoring is achieved without introducing additional desolvation resistance or increasing electrolyte viscosity at low temperatures due to an excessively high proportion of cosolvent, nor is it necessary to disrupt the equilibrium of the solvated structure due to excessive volatilization of the cosolvent at high temperatures. More importantly, a reasonable concentration and ratio ensures that the solvated structure does not undergo drastic recombination or dissociation during temperature rises and falls. 2+ The solvation-desolventization equilibrium remains favorable for rapid charge transfer over a wide temperature range. Meanwhile, the lower LUMO energy level of the pyrazole cosolvent allows for the in-situ generation of C-rich compounds on the magnesium anode surface. x N yThe solid electrolyte interface layer, with its alternating organic and inorganic components, exhibits high thermodynamic stability. This dense structure does not undergo thermal decomposition or structural collapse at high temperatures, nor does it crack or peel due to thermal stress contraction at low temperatures, thus continuously functioning as a barrier between the electrolyte and the reactive magnesium metal. A portion of the ionicly conductive compound in this interface layer is Mg. 2+ It provides a continuous transport channel, compensating for insufficient interfacial supply caused by decreased ion migration rate at low temperatures, and ensuring Mg at high temperatures. 2+ The rapid supply at the interface is not affected by changes in transport resistance. Furthermore, the nitrogen-containing heterocyclic cosolvent and TFSI... - The interaction between them remains stable over a wide temperature range, and is also effective for TFSI. - The anchoring effect is not significantly weakened by temperature fluctuations, thus continuously suppressing TFSI under both low and high temperature conditions. - Irreversible decomposition and passivation layer formation. From a more macroscopic synergistic perspective, solvation structure regulation, interface layer protection, and TFSI... - The three anchoring elements form a multi-layered functional synergy across the temperature dimension: the solvation structure maintains relative stability with temperature changes, ensuring the stability of Mg. 2+ The desolvation kinetics are not significantly degraded by temperature fluctuations; C x N y The interface layer maintains its structural integrity under temperature fluctuations, providing a continuous physical protective barrier and ion transport channels for the electrode surface; TFSI - The temperature insensitivity of the anchoring effect ensures the continued effectiveness of the passivation suppression mechanism across a wide temperature range. The combined effect of these three factors allows the reduction of the desolvation barrier, the suppression of the passivation layer, and the mechanical protection of the interface to operate synergistically under different temperature conditions. Ultimately, this ensures that the electrolyte maintains stable electrochemical performance across a wide temperature range of -10℃ to 80℃, providing a reliable electrolyte solution for the practical application of magnesium batteries under extreme temperature conditions.

[0091] (4) Full battery charge and discharge test

[0092] The electrolyte prepared in Example 1 was subjected to a full-cell charge-discharge test, i.e., a constant current charge-discharge (CP) test. The test was conducted by assembling a CR2032 coin cell, with Mo6S8 as the positive electrode, carbon paper (CF) as the substrate, magnesium sheet as the negative electrode, glass fiber membrane (GF / A) as the separator, and a current of 3C.

[0093] The Mg||Mo6S8 full cell stably cycled 9000 times at a high current density of 3C, while maintaining a capacity of 75 mAh / g. Figure 6As shown, at a high current density of 3C, this full cell can stably cycle 9000 times, maintaining a discharge capacity of 75 mAh / g. Furthermore, the capacity decay during cycling is gradual, without significant periodic drops or accelerated degradation. This high-rate, long-cycle performance is a comprehensive manifestation of the aforementioned technological effects within the full cell system. The reduction in the desolvation energy barrier allows Mg... 2+ It can still rapidly complete interfacial charge transfer under high current conditions, avoiding the exacerbation of interfacial polarization caused by sluggish desolvation kinetics; TFSI - The effective suppression of the passivation layer ensures that both the positive and negative electrode surfaces have sufficient electrochemical active sites, allowing Mg... 2+ The insertion and extraction process is not constrained by the increase in interface impedance at high magnification; C x N y The compound with ionic conductivity in the interface layer is Mg. 2+ It provides a continuous transmission channel, ensuring the quality of Mg. 2+ Rapid supply at the interface can meet the requirements of high-current discharge. The three effects mentioned above form a closer synergistic relationship under high-rate operating conditions: improved desolvation kinetics ensure that Mg... 2+ Deposition can be completed rapidly after crossing the interface layer, and the ionicly conductive components in the interface layer ensure the stability of Mg. 2+ The rapid supply at the interface, together with the co-solvent, maintained the steady-state operation of the interfacial electrochemical process at high current densities. Furthermore, the uniform deposition characteristics achieved by the electrostatic shielding effect of the pyrazole co-solvent also played a crucial role in high-rate cycling, preventing dendrite growth caused by localized current concentration at high current densities and its mechanical damage to the SEI layer. This allowed the full cell to maintain structural integrity and electrochemical activity even after 9000 high-rate cycles. In summary, performance verification from symmetric cells to full cells and from low current to high rate demonstrates that the electrolyte system of this invention, through a co-solvent competitive coordination strategy, achieves effective synergistic protection mechanisms in different electrochemical scenarios for solvation structure regulation, in-situ construction of the interfacial layer, and dendrite growth inhibition. Ultimately, this resulted in an ultra-long cycle life and stable capacity retention at high rates. Examples 2-7, after undergoing the above electrochemical performance tests, showed little difference in performance from Example 1, and will not be repeated here. In conclusion, the electrolyte of this invention exhibits long cycle stability, high magnesium deposition / dissolution efficiency, and wide temperature tolerance.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the technical solutions. Those skilled in the art should understand that any modifications or equivalent substitutions to the technical solutions of the present invention without departing from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A magnesium battery electrolyte with ultra-long lifespan and ultra-low overpotential over a wide temperature range, characterized in that, The electrolyte is composed of magnesium salt, nitrogen-containing heterocyclic cosolvent, and organic solvent; Wherein, the magnesium salt is bis(trifluoromethanesulfonylimide)magnesium; the nitrogen-containing heterocyclic cosolvent is any one of 1-methylpyrazole, 1-ethylpyrazole, 1-propylpyrazole, 1-methyl-3-trifluoromethyl-1H-pyrazole, 1-ethyl-3-trifluoromethyl-1H-pyrazole, and 1-propyl-3-trifluoromethyl-1H-pyrazole; the organic solvent is any one of 3-methoxypropylamine, 2-methoxyethylamine, 3-methoxyisopropylamine, 1-methoxypropyldiamine, 3-isopropoxypropylamine, ethylene glycol dimethyl ether, or tetrahydrofuran; In the organic solvent, the concentration of magnesium salt is 0.1 mol / L to 0.4 mol / L, and the volume ratio of nitrogen-containing heterocyclic cosolvent to organic solvent is (1:19) to (1:10).

2. The ultra-long lifespan and ultra-low overpotential wide-temperature range magnesium battery electrolyte according to claim 1, characterized in that, The electrolyte is prepared by the following steps: Step 1: Dissolve the magnesium salt in an organic solvent and mix thoroughly at 20℃~25℃ to obtain a mixed solution; Step 2: Add a nitrogen-containing heterocyclic co-solvent to the mixed solution obtained in Step 1, and stir to obtain the electrolyte.

3. The ultra-long lifespan and ultra-low overpotential wide-temperature range magnesium battery electrolyte according to claim 2, characterized in that, Both steps 1 and 2 are performed in an inert gas atmosphere.

4. The ultra-long lifespan and ultra-low overpotential wide-temperature range magnesium battery electrolyte according to claim 2, characterized in that, In the mixing system of steps 1 and 2, the water content and oxygen content are both less than 0.01 ppm.

5. The ultra-long lifespan and ultra-low overpotential wide-temperature range magnesium battery electrolyte according to claim 2, characterized in that, The magnesium salt was pretreated as follows: The magnesium salt was vacuum dried at 70℃~90℃ for at least 24 hours and then sealed for storage.

6. The ultra-long lifespan and ultra-low overpotential wide-temperature range magnesium battery electrolyte according to claim 2, characterized in that, The organic solvent is pretreated as follows: The molecular sieve is heated to 300℃~400℃ and activated for 4~6 hours, then added to the organic solvent and sealed for storage.

7. A rechargeable magnesium battery, characterized in that, The electrolyte in the rechargeable magnesium battery is the ultra-long life and ultra-low overpotential wide temperature range magnesium battery electrolyte as described in any one of claims 1 to 6.

8. The rechargeable magnesium battery according to claim 7, characterized in that, The rechargeable magnesium battery can operate stably in a wide temperature range of -10℃ to 80℃.

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