Wide-temperature electrolyte and preparation method and application thereof

Abstract

The invention belongs to the technical field of battery electrolyte, and discloses wide-temperature electrolyte as well as a preparation method and application thereof. The wide-temperature electrolyte comprises a solvent, an additive and a metal salt, the metal salts comprise two lithium salts or two sodium salts; the solvent comprises at least two carbonic ester solvents with asymmetric structures, optionally carboxylic ester solvents with asymmetric structures and optionally nitrile solvents with asymmetric structures; according to the wide-temperature electrolyte provided by the invention, an asymmetric structure of the solvent and the lithium salt is utilized, so that a battery applying the wide-temperature electrolyte shows good temperature stability and cycling stability in a temperature range of-80 DEG C to 80 DEG C.

Description

Technical Field

[0001] The present invention relates to the technical field of battery electrolytes, and in particular to a wide-temperature electrolyte and a preparation method and application thereof. Background Art

[0002] Batteries, as advanced energy storage devices, have seen a growing number of applications since their introduction. Lithium-ion batteries, with their advantages such as small size, high energy density, low self-discharge, no memory effect, and low cost, have rapidly captured the market in consumer electronics, energy storage, and electric vehicles. As batteries continue to penetrate deeper into everyday life and production, their diverse application scenarios are also expanding, and their stable operation and storage across a wide temperature range are attracting widespread attention. Currently, however, the optimal operating temperature for conventional commercial lithium-ion batteries is 15-35°C. Temperatures both higher and lower can degrade battery performance and even pose safety concerns. This narrow temperature range severely limits the battery's application in specific environments. For example, consumer electronics require normal operation within a temperature range of -20-45°C; energy storage and electric vehicles require operation within a wide temperature range of -30-52°C; and polar, deep-sea, and space exploration impose even more stringent requirements on battery stability over a wide temperature range.

[0003] Conventional lithium-ion batteries degrade under different conditions at high and low temperatures. High temperatures present challenges such as severe electrolyte side reactions, dissolution and regeneration of the solid electrolyte interface (SEI), transition metal dissolution, and increased gassing. Low temperatures primarily impact the decline in molecular dynamics, such as ion migration and charge transfer. These issues are closely linked to the electrolyte, the lifeblood of the battery, and electrolyte design offers significant advantages in terms of cost, feasibility, and efficiency.

[0004] Due to the high melting point of ethylene carbonate (EC) solvent, the operating temperature range of currently used electrolyte systems is limited to -20-60°C, which to some extent restricts the use of batteries, especially lithium batteries. Therefore, developing an electrolyte with a wide temperature range is of great significance to broaden the application range of batteries, especially lithium batteries. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that the electrolytes used in existing batteries, especially lithium batteries, have a narrow operating temperature range, poor cycle stability and high production costs. A wide-temperature electrolyte and its preparation method and application are provided. By adopting a combination of at least two solvents with asymmetric structures and optionally a solvent with a symmetric structure, the purpose of lowering the freezing point of the electrolyte and aggravating the supercooling phenomenon is achieved, thereby slowing down the electrolyte coagulation process, thereby ensuring the high-temperature stability of the electrolyte while broadening its application under extreme low temperature conditions (≤-30°C).

[0006] In order to solve the above technical problems, the first aspect of the present invention provides a wide temperature range electrolyte, comprising a solvent, an additive and a metal salt; The metal salt comprises two lithium salts or two sodium salts; The solvent comprises at least two asymmetric carbonate solvents and optionally an asymmetric carboxylate solvent, and optionally an asymmetric nitrile solvent.

[0007] In the present invention, the solvent includes at least two carbonate solvents with asymmetric structures, which can take into account both high boiling point and low freezing point.

[0008] In the present invention, "asymmetric structure" means that the structural formula of the solvent is asymmetric, for example, the structural formula of ethyl methyl carbonate is Similarly, "symmetrical structure" refers to the symmetry of the solvent's structural formula, such as the structural formula of ethylene carbonate .

[0009] According to some embodiments of the present invention, the total concentration of the metal salt in the wide temperature electrolyte is 0.5 mol / L to 2.5 mol / L.

[0010] According to some embodiments of the present invention, the molar ratio of the two lithium salts or the two sodium salts is (1:6)-(6:1).

[0011] According to some embodiments of the present invention, the additive is added in an amount of 3 wt % to 5 wt % of the total mass of the solvent and the metal salt.

[0012] According to some embodiments of the present invention, the carbonate solvent with an asymmetric structure accounts for 70% to 100% of the total volume of the solvent, preferably 70% to 90%.

[0013] According to some embodiments of the present invention, the asymmetric carbonate solvent is selected from at least two of ethyl methyl carbonate, methyl propyl carbonate, propylene carbonate, and fluoroethylene carbonate; preferably, the asymmetric carbonate solvent is selected from a combination of ethyl methyl carbonate and propylene carbonate or a combination of methyl propyl carbonate and propylene carbonate, and the volume ratio of ethyl methyl carbonate and propylene carbonate or methyl propyl carbonate and propylene carbonate is (6-7):1.

[0014] In the present invention, the carbonate solvent with an asymmetric structure can reduce the freezing point and intensify the supercooling phenomenon through the asymmetric structure while taking into account high temperature, thereby realizing the application of the electrolyte in a wide temperature range.

[0015] According to some embodiments of the present invention, the asymmetric carboxylate solvent is selected from at least one of methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, ethyl propionate, and ethyl isobutyrate.

[0016] In the present invention, the carboxylic acid ester solvents with asymmetric structures generally have a low freezing point and a low desolvation energy barrier, which can broaden the high-temperature application range of the electrolyte.

[0017] According to some embodiments of the present invention, the asymmetric nitrile solvent is selected from butyronitrile and / or 3-methoxypropionitrile.

[0018] According to some embodiments of the present invention, the carbonate solvent with a symmetrical structure is selected from at least one of ethylene carbonate, dimethyl carbonate, diethyl carbonate, and vinyl sulfite.

[0019] According to some embodiments of the present invention, the carbonate solvent with a symmetrical structure accounts for 0-30% of the total volume of the solvent, preferably 10% to 30%.

[0020] According to some embodiments of the present invention, the solvent includes two asymmetric carbonate solvents, a symmetric carbonate solvent and optionally an asymmetric carboxylate solvent; preferably, the volume ratio of the asymmetric carbonate solvent to the asymmetric carboxylate solvent and the symmetric carbonate solvent is (6-7):1:(0-1):(1-2).

[0021] According to some embodiments of the present invention, the lithium salt is selected from at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium bis(oxalatoborate) (LiBOB), lithium difluorooxalatoborate (LiDFOB), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium difluorophosphate (LiPO2F2), lithium difluorobis(oxalatophosphate) (LiODPF), lithium hexafluoroarsenate (LiAsF6) and lithium perchlorate (LiClO4).

[0022] According to some embodiments of the present invention, the sodium salt is selected from at least one of sodium hexafluorophosphate (NaPF6), sodium tetrafluoroborate (NaBF4), sodium bis(oxalatoborate) (NaBOB), sodium difluorooxalatoborate (NaDFOB), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), sodium bis(fluorosulfonyl)imide (NaFSI), sodium difluorophosphate (NaPO2F2), sodium difluorobis(oxalatophosphate) (NaODPF), sodium hexafluoroarsenate (NaAsF6) and sodium perchlorate (NaClO4).

[0023] According to some embodiments of the present invention, the additive is selected from at least two of fluoroethylene carbonate, vinyl sulfate, vinylene carbonate, 1,3-propane sultone, methylene methanedisulfonate, and tris(trimethylsilyl)phosphate; preferably, the additive is a combination of fluoroethylene carbonate and vinyl sulfate in a mass ratio of (2-3):1.

[0024] In the present invention, by using a high-entropy combination of an asymmetric solvent and a metal salt, the thermodynamic and kinetic processes of electrolyte solidification are regulated, the freezing point of the electrolyte is lowered and the supercooling phenomenon is aggravated, and the battery can operate stably in a wide temperature range of -80°C to 80°C; the specific principle of regulating the thermodynamic and kinetic processes of electrolyte solidification is: solidification is a process in which thermodynamics and kinetics act together. Thermodynamically, a solvent with an asymmetric structure can reduce intermolecular interactions, thereby reducing the solidification enthalpy change ΔH of the solvent, and the high-entropy combination of an asymmetric solvent and a metal salt can also increase the solidification entropy change ΔS of the electrolyte system, thereby achieving the effect of lowering the freezing point of the electrolyte; kinetically, the ordered arrangement of the solvent with an asymmetric structure is slower during the solidification process, because the solvent with an asymmetric structure rotates or migrates more slowly than the solvent with a symmetric structure, thereby achieving the purpose of lowering the freezing point of the electrolyte and aggravating the supercooling phenomenon.

[0025] A second aspect of the present invention provides a method for preparing the above-mentioned wide-temperature electrolyte, comprising mixing a metal salt, a solvent, and an additive to obtain the wide-temperature electrolyte.

[0026] According to some embodiments of the present invention, the method for preparing the wide-temperature electrolyte comprises the following steps: Step 1: In a glove box or a dry room with a humidity of less than 10%, the solvents of the asymmetric structures are mixed and stirred at room temperature to obtain a mixed solvent; Step 2: Add metal salt and additives to the mixed solvent obtained in step 1, and stir at room temperature for 6 hours to obtain the wide temperature electrolyte of the present invention.

[0027] In the present invention, when the solvents are mixed, the stirring conditions are not particularly limited, and all of them are conventional technical means known to those skilled in the art; in the present invention, when the mixed solvent is mixed with the metal salt and the additive, the stirring conditions are not particularly limited, and all of them are conventional technical means known to those skilled in the art, for example, stirring at room temperature for 6 hours to completely dissolve the metal salt.

[0028] According to some embodiments of the present invention, the mixing is performed in a glove box or under conditions where the humidity is less than 10%.

[0029] According to some embodiments of the present invention, the application temperature of the wide temperature electrolyte is -80°C to 80°C.

[0030] A third aspect of the present invention provides a use of the wide temperature range electrolyte provided by the first aspect or the wide temperature range electrolyte prepared by the preparation method provided by the second aspect in a lithium ion battery or a lithium metal battery.

[0031] A fourth aspect of the present invention provides a use of the wide temperature range electrolyte provided by the first aspect or the wide temperature range electrolyte prepared by the preparation method provided by the second aspect in a lithium ion battery or a lithium metal battery.

[0032] Beneficial effects: The wide-temperature electrolyte provided by the present invention utilizes the asymmetric structure of the solvent and the lithium salt, so that the battery using the wide-temperature electrolyte of the present invention exhibits good temperature stability and cycle stability in the temperature range of -80°C to 80°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of the effect of asymmetric solvent (ethyl methyl carbonate) on freezing point; Figure 2 This is a cycle diagram of the wide-temperature electrolyte prepared in Example 1 of the present invention at -60°C; Figure 3 This is a cycle diagram of the wide-temperature electrolyte prepared in Example 1 of the present invention at 70°C; Figure 4 This is a cycle diagram of the wide-temperature electrolyte prepared in Example 2 of the present invention at -60°C; Figure 5 This is a cycle diagram of the wide-temperature electrolyte prepared in Example 2 of the present invention at 70°C; Figure 6 This is a cycle diagram of the wide-temperature electrolyte prepared in Example 3 of the present invention at -60°C; Figure 7 This is a cycle diagram of the wide-temperature electrolyte prepared in Example 3 of the present invention at 70°C; Figure 8 This is a cycle diagram of the wide-temperature electrolyte prepared in Comparative Example 1 of the present invention at 70°C. DETAILED DESCRIPTION

[0034] The present invention will be further described below with reference to the following examples, but the present invention is not limited to these examples.

[0035] In the following examples and comparative examples of the present invention, unless otherwise specified, all raw materials used are commercially available.

[0036] In the present invention, the normal temperature condition is 25° C. unless otherwise specified.

[0037] Example 1 This embodiment is used to illustrate the wide temperature range electrolyte and its preparation method of the present invention.

[0038] The solvent of the wide-temperature electrolyte is a combination of methyl propyl carbonate, propylene carbonate and 3-methoxypropionitrile in a volume ratio of 7:1:2; the lithium salt is lithium bis(fluorosulfonyl)imide (LiFSI) and lithium hexafluorophosphate (LiPF6) in a molar ratio of 1:6; and the additives are fluoroethylene carbonate and vinyl sulfate in a mass ratio of 2:1.

[0039] The preparation method of the wide temperature electrolyte is as follows: Step 1: In a glove box, methyl propyl carbonate, propylene carbonate, and 3-methoxypropionitrile are stirred uniformly at room temperature to obtain a mixed solvent; Step 2: Add lithium bis(fluorosulfonyl)imide (LiFSI) and lithium hexafluorophosphate (LiPF6), as well as fluoroethylene carbonate and vinyl sulfate to the mixed solvent obtained in step 1, and stir at room temperature for 6 hours to obtain the wide temperature electrolyte of the present invention, wherein the total concentration of lithium salt is 1 mol / L, and the amount of additive added is 3 wt% of the total mass of the solvent and lithium salt.

[0040] This embodiment continues to provide a lithium metal battery, whose electrolyte adopts the wide-temperature electrolyte prepared in the above embodiment 1. After the lithium metal battery is activated by a 0.1C current charge and discharge, a low-temperature cycle test is performed with a current of 0.1C charge / 0.3C discharge, and a high-temperature cycle test is performed with a current of 1C charge and discharge, with a cut-off voltage range of 2.0-4.0V.

[0041] The test results show that the lithium metal battery can maintain a capacity of 75.4% after 10 cycles at -60°C, and 94.7% after 100 cycles at 70°C. The low-temperature (-60°C) cycle diagram and the high-temperature (70°C) cycle diagram are shown as follows: Figure 2 and Figure 3 shown.

[0042] Example 2 This embodiment is used to illustrate the wide temperature range electrolyte and its preparation method of the present invention.

[0043] The solvent of the wide-temperature electrolyte is a combination of ethyl methyl carbonate, propylene carbonate, ethyl isobutyrate and ethylene carbonate in a volume ratio of 6:1:1:2; the lithium salt is lithium bis(fluorosulfonyl)imide (LiFSI) and lithium difluorobis(oxalophosphate) (LiODPF) in a molar ratio of 6:1; and the additives are fluoroethylene carbonate and vinyl sulfate in a mass ratio of 2:1.

[0044] The preparation method of the wide temperature electrolyte is as follows: Step 1: In a glove box, ethyl methyl carbonate, propylene carbonate, ethyl isobutyrate, and ethylene carbonate are stirred uniformly at room temperature to obtain a mixed solvent; Step 2: Add lithium bis(fluorosulfonyl)imide (LiFSI) and lithium difluorobis(oxalophosphate) (LiODPF), as well as fluoroethylene carbonate and vinyl sulfate to the mixed solvent obtained in step 1, and stir at room temperature for 6 hours to obtain the wide temperature electrolyte of the present invention, wherein the total concentration of lithium salt is 1 mol / L, and the amount of additive added is 3 wt% of the total mass of the solvent and lithium salt.

[0045] This embodiment continues to provide a lithium metal battery, whose electrolyte adopts the wide-temperature electrolyte prepared in the above embodiment 2. After the lithium metal battery is activated by a 0.1C current charge and discharge, a low-temperature cycle test is performed with a current of 0.1C charge / 0.3C discharge, and a high-temperature cycle test is performed with a current of 1C charge and discharge, with a cut-off voltage range of 2.0-4.0V.

[0046] The test results show that the lithium metal battery can maintain a capacity of 75.8% after 10 cycles at -60°C, and 95.2% after 100 cycles at 70°C. The low-temperature (-60°C) and high-temperature (70°C) cycle diagrams are shown as follows: Figure 4 and Figure 5 shown.

[0047] Example 3 This embodiment is used to illustrate the wide temperature range electrolyte and its preparation method of the present invention.

[0048] The solvent of the wide-temperature electrolyte is a combination of methyl propyl carbonate, propylene carbonate and fluoroethylene carbonate in a volume ratio of 7:1:2; the sodium salt is sodium bis(fluorosulfonyl)imide (NaFSI) and sodium hexafluorophosphate (NaPF6) in a molar ratio of 1:6; and the additives are fluoroethylene carbonate and vinyl sulfate in a mass ratio of 2:1.

[0049] The preparation method of the wide temperature electrolyte is as follows: Step 1: In a glove box, methyl propyl carbonate, propylene carbonate and fluoroethylene carbonate are stirred uniformly at room temperature to obtain a mixed solvent; Step 2: Add sodium bis(fluorosulfonyl)imide (NaFSI) and sodium hexafluorophosphate (NaPF6), as well as fluoroethylene carbonate and vinyl sulfate to the mixed solvent obtained in step 1, and stir at room temperature for 6 hours to obtain the wide temperature electrolyte of the present invention, wherein the total concentration of sodium salt is 1 mol / L, and the amount of additive added is 3 wt% of the total mass of the solvent and sodium salt.

[0050] This embodiment further provides a sodium metal battery, wherein the electrolyte used is the wide-temperature electrolyte prepared in the above embodiment 2. The sodium metal battery is activated by a single charge and discharge current of 0.1C, and then subjected to a low-temperature cycle test with a charge current of 0.1C / discharge current of 0.3C, and a high-temperature cycle test with a charge and discharge current of 1C, with a cutoff voltage range of 2.0-4.0V.

[0051] The test results show that the sodium metal battery can maintain a capacity of 79.8% after 10 cycles at -60°C, and 91.5% after 100 cycles at 70°C. The low-temperature (-60°C) and high-temperature (70°C) cycle diagrams are shown below. Figure 6 and Figure 7 shown.

[0052] Example 4 This embodiment is used to illustrate the wide temperature range electrolyte and its preparation method of the present invention.

[0053] The preparation method of the wide-temperature electrolyte is the same as that of Example 2, except that an equal volume of methyl propyl carbonate is used instead of methyl ethyl carbonate.

[0054] This embodiment continues to provide a lithium metal battery, whose electrolyte adopts the electrolyte prepared in the above embodiment 4. After the lithium metal battery is activated by a 0.1C current charge and discharge, a low-temperature cycle test is performed with a current of 0.1C charge / 0.3C discharge, and a high-temperature cycle test is performed with a current of 1C charge and discharge, with a cut-off voltage range of 2.0-4.0V.

[0055] The test results show that the lithium metal battery can maintain a capacity of 75.6% after 10 cycles at -60°C, and can maintain a capacity of 95.0% after 100 cycles at 70°C.

[0056] Example 5 This embodiment is used to illustrate the wide temperature range electrolyte and its preparation method of the present invention.

[0057] The preparation method of the wide temperature electrolyte is the same as that of Example 2; the difference is that the solvent of the wide temperature electrolyte is a combination of ethyl methyl carbonate, propylene carbonate, ethyl isobutyrate and ethylene carbonate in a volume ratio of 6:1:2:1.

[0058] This embodiment continues to provide a lithium metal battery, whose electrolyte adopts the electrolyte prepared in the above embodiment 5. After the lithium metal battery is activated by a 0.1C current charge and discharge, a low-temperature cycle test is performed with a current of 0.1C charge / 0.3C discharge, and a high-temperature cycle test is performed with a current of 1C charge and discharge, with a cut-off voltage range of 2.0-4.0V.

[0059] The test results show that the lithium metal battery has a capacity retention rate of 74.2% after 10 cycles at a temperature of -60°C and a capacity retention rate of 94.9% after 100 cycles at a temperature of 70°C.

[0060] Example 6 This example is used to illustrate the wide-temperature electrolyte and the preparation method thereof.

[0061] The preparation method of the wide-temperature electrolyte is the same as that in Example 2, except that the solvent of the wide-temperature electrolyte is a combination of methyl ethyl carbonate, propylene carbonate, ethyl isobutyrate and vinyl carbonate at a volume ratio of 7:1:0:2.

[0062] This example continues to provide a lithium metal battery, the electrolyte of which is the electrolyte prepared in Example 6 described above. After the lithium metal battery is activated by 0.1C current charging and discharging once, the lithium metal battery is subjected to low-temperature cycle test at a current of 0.1C charging / 0.3C discharging and high-temperature cycle test at a current of 1C charging and discharging, and the voltage range is 2.0-4.0V.

[0063] The test results show that the lithium metal battery has a capacity retention rate of 74.2% after 10 cycles at a temperature of -60°C and a capacity retention rate of 94.9% after 100 cycles at a temperature of 70°C.

[0064] Comparative Example 1 This comparative example is used to illustrate an electrolyte and a preparation method thereof.

[0065] In the comparative example, the solvent of the electrolyte is a combination of vinyl carbonate, dimethyl carbonate and methyl ethyl carbonate at a volume ratio of 3:3:4; the lithium salt is lithium bisfluorosulfonylimide (LiFSI) and lithium hexafluorophosphate (LiPF6) at a molar ratio of 1:6; and the additives are fluoroethylene carbonate and ethylene sulfate at a mass ratio of 2:1.

[0066] The preparation method of the electrolyte is as follows: Step one, in a glove box, uniformly stir vinyl carbonate, dimethyl carbonate and methyl ethyl carbonate at room temperature to obtain a mixed solvent; Step two, add lithium bisfluorosulfonylimide (LiFSI) and lithium hexafluorophosphate (LiPF6) and fluoroethylene carbonate and ethylene sulfate to the mixed solvent obtained in step one, and stir at room temperature for 6h to obtain an electrolyte, wherein the total concentration of lithium salt is 1mol / L, and the amount of additives is 3wt% of the total mass of the solvent and the lithium salt.

[0067] This comparative example continues to provide a lithium metal battery, whose electrolyte adopts the electrolyte prepared in the above comparative example 1. After the lithium metal battery is activated by a 0.1C current charge and discharge, a low-temperature cycle test is performed with a current of 0.1C charge / 0.3C discharge, and a high-temperature cycle test is performed with a current of 1C charge and discharge, with a cut-off voltage range of 2.0-4.0V.

[0068] The test results show that the lithium metal battery can maintain a capacity of 0% (electrolyte solidifies) after 10 cycles at -60°C, and 78.5% after 100 cycles at 70°C. The high temperature (70°C) cycle diagram is shown below. Figure 8 shown.

[0069] Comparative Example 2 This comparative example is used to illustrate the wide temperature range electrolyte and its preparation method of the present invention.

[0070] The preparation method of the wide-temperature electrolyte is the same as that of Example 2, except that the solvent of the wide-temperature electrolyte is a combination of ethyl methyl carbonate, ethyl isobutyrate, and ethylene carbonate in a volume ratio of 7:1:2.

[0071] This comparative example continues to provide a lithium metal battery, whose electrolyte adopts the electrolyte prepared in the above comparative example 2. After the lithium metal battery is activated by a 0.1C current charge and discharge, a low-temperature cycle test is performed with a current of 0.1C charge / 0.3C discharge, and a high-temperature cycle test is performed with a current of 1C charge and discharge, with a cut-off voltage range of 2.0-4.0V.

[0072] The test results show that the lithium metal battery can retain its capacity at 0% (electrolyte solidifies) after 10 cycles at -60°C, and at 70°C after 100 cycles, its capacity retention can reach 77.2%.

[0073] Comparative Example 3 This comparative example is used to illustrate the wide temperature range electrolyte and its preparation method of the present invention.

[0074] The preparation method of the wide-temperature electrolyte is the same as that of Example 2, except that the solvent of the wide-temperature electrolyte is a combination of propylene carbonate, ethyl isobutyrate and ethylene carbonate in a volume ratio of 7:1:2.

[0075] This comparative example continues to provide a lithium metal battery, whose electrolyte adopts the electrolyte prepared in the above comparative example 2. After the lithium metal battery is activated by a 0.1C current charge and discharge, a low-temperature cycle test is performed with a current of 0.1C charge / 0.3C discharge, and a high-temperature cycle test is performed with a current of 1C charge and discharge, with a cut-off voltage range of 2.0-4.0V.

[0076] The test results show that the lithium metal battery can retain its capacity at 0% (electrolyte solidifies) after 10 cycles at -60°C, and at 69.8% after 100 cycles at 70°C.

[0077] Comparative Example 4 This comparative example is used to illustrate the wide temperature range electrolyte and its preparation method of the present invention.

[0078] The preparation method of the wide-temperature electrolyte is the same as that of Example 1, except that the solvent of the wide-temperature electrolyte is a combination of ethyl methyl carbonate, propylene carbonate, ethyl isobutyrate and ethylene carbonate in a volume ratio of 5:1:1:3.

[0079] This comparative example continues to provide a lithium metal battery, whose electrolyte adopts the electrolyte prepared in the above comparative example 3. After the lithium metal battery is activated by a 0.1C current charge and discharge, a low-temperature cycle test is performed with a current of 0.1C charge / 0.3C discharge, and a high-temperature cycle test is performed with a current of 1C charge and discharge, with a cut-off voltage range of 2.0-4.0V.

[0080] The test results show that the lithium metal battery can retain its capacity at 0% (electrolyte solidifies) after 10 cycles at -60°C, and at 70°C after 100 cycles, its capacity retention can reach 75.6%.

[0081] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation of the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A wide temperature electrolyte, characterized in that: including solvents, additives and metal salts; The metal salt comprises two lithium salts or two sodium salts; The solvent comprises at least two asymmetric carbonate solvents and optionally an asymmetric carboxylate solvent, and optionally an asymmetric nitrile solvent.

2. The wide temperature electrolyte according to claim 1, characterized in that The total concentration of the metal salt in the wide temperature electrolyte is 0.5 mol / L to 2.5 mol / L; and / or, the molar ratio of the two lithium salts or the two sodium salts is (1-6):(6-1); and / or, the amount of the additive is 3 wt% to 5 wt% of the total mass of the solvent and the metal salt; And / or, the carbonate solvent with an asymmetric structure accounts for 70% to 100% of the total volume of the solvent, preferably 70% to 90%.

3. The wide temperature electrolyte according to claim 1 or 2, characterized in that The asymmetric carbonate solvent is selected from at least two of ethyl methyl carbonate, methyl propyl carbonate, propylene carbonate, and fluoroethylene carbonate; preferably, the asymmetric carbonate solvent is selected from a combination of ethyl methyl carbonate and propylene carbonate or a combination of methyl propyl carbonate and propylene carbonate, and the volume ratio of ethyl methyl carbonate and propylene carbonate or methyl propyl carbonate and propylene carbonate is (6-7):1; And / or, the asymmetric carboxylate solvent is selected from at least one of methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, ethyl propionate, and ethyl isobutyrate; And / or, the asymmetric nitrile solvent is selected from butyronitrile and / or 3-methoxypropionitrile.

4. The wide temperature electrolyte according to any one of claims 1 to 3, characterized in that The solvent also includes a carbonate solvent of an optionally symmetrical structure; Preferably, the carbonate solvent with a symmetrical structure is selected from at least one of ethylene carbonate, dimethyl carbonate and diethyl carbonate; More preferably, the carbonate solvent with a symmetrical structure accounts for 0-30% of the total volume of the solvent, preferably 10% to 30%.

5. The wide temperature electrolyte according to claim 4, characterized in that The solvent comprises two asymmetric carbonate solvents, a symmetric carbonate solvent and optionally an asymmetric carboxylate solvent; preferably, the volume ratio of the asymmetric carbonate solvent to the asymmetric carboxylate solvent and the symmetric carbonate solvent is (6-7):1:(0-1):(1-2).

6. The wide temperature electrolyte according to any one of claims 1 to 5, characterized in that The lithium salt is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium bis(trifluoromethanesulfonylimide), lithium bis(fluorosulfonylimide), lithium difluorophosphate, lithium difluorobis(oxalatophosphate), lithium hexafluoroarsenate and lithium perchlorate; and / or, the sodium salt is at least one selected from sodium hexafluorophosphate, sodium tetrafluoroborate, sodium bisoxalatoborate, sodium difluorooxalatoborate, sodium bistrifluoromethanesulfonyl imide, sodium bisfluorosulfonyl imide, sodium difluorophosphate, sodium difluorobisoxalatophosphate, sodium hexafluoroarsenate, and sodium perchlorate; And / or, the additive is selected from at least two of fluoroethylene carbonate, vinyl sulfate, vinylene carbonate, 1,3-propane sultone, methylene methanedisulfonate, and tris(trimethylsilyl)phosphate; preferably, the additive is a combination of fluoroethylene carbonate and vinyl sulfate in a mass ratio of (2-3):

1.

7. A method for preparing the wide temperature electrolyte according to any one of claims 1 to 6, characterized in that: The method comprises mixing a metal salt, a solvent and an additive to obtain the wide-temperature electrolyte.

8. The preparation method according to claim 7, characterized in that The mixing is performed in a glove box or under a condition where the humidity is less than 10%.

9. Use of the wide temperature electrolyte according to any one of claims 1 to 5 or the wide temperature electrolyte prepared by the preparation method according to claim 6 or 7 in a lithium ion battery or a lithium metal battery.

10. Use of the wide temperature electrolyte according to any one of claims 1 to 5 or the wide temperature electrolyte prepared by the preparation method according to claim 6 or 7 in a sodium ion battery or a sodium metal battery.

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