Alkali metal battery cyclic ether electrolyte, preparation method thereof and alkali metal battery

Abstract

The invention discloses a cyclic ether electrolyte for an alkali metal battery. The cyclic ether electrolyte comprises a lithium salt, a sodium salt and a specific cyclic ether solvent, wherein the specific cyclic ether has a cyclic structure and contains a branched chain, and each of the cyclic structure and the branched chain contains at least one oxygen atom. The problems of poor high voltage resistance and insufficient alkali metal stability of a linear ether solvent in an alkali metal battery are solved in a targeted manner. In a high-voltage alkali metal battery, the prepared cyclic ether electrolyte shows excellent electrochemical stability, a LiNCM811 battery can still operate stably after being circulated for 300 circles under the condition of 4.3 V, the capacity retention rate reaches up to 81.1%, the problem that a linear ether electrolyte cannot operate in a high-voltage alkali metal battery system is solved, and the performance of the lithium ion battery is improved. And the development of the cyclic ether electrolyte in an alkali metal battery system is promoted.

Description

Technical Field

[0001] The invention belongs to the technical field of battery electrolytes, and in particular relates to an alkali metal battery cyclic ether electrolyte and a preparation method thereof, and an alkali metal battery. Background Art

[0002] Alkali metal batteries are battery technologies that use alkali metal elements (such as lithium, sodium, potassium, etc.) as negative electrode materials. They have attracted much attention due to their high energy density and high voltage characteristics. Among them, lithium metal batteries are considered to be one of the most promising energy storage systems, with extremely high theoretical specific capacity (3860mAh g -1 ) and the lowest electrode potential (-3.04V relative to the standard hydrogen electrode). When matched with ternary cathode materials, the battery energy density can reach 500Wh kg -1 When sulfur is used as the positive electrode material, the theoretical energy density of the battery can exceed 500Wh kg -1 . However, lithium metal anodes have a series of problems such as lithium dendrite growth, electrolyte decomposition, and low coulombic efficiency, which lead to a short cycle life of the battery, seriously restricting the commercial application of lithium batteries. In addition, sodium metal batteries are considered to be a highly promising energy storage technology because they use sodium metal to replace lithium metal. However, sodium metal batteries and lithium metal batteries have common problems such as negative electrode stability.

[0003] Linear ether electrolytes are widely used in lithium / sodium metal battery systems due to their good compatibility with alkali metal negative electrodes, high ionic conductivity, low viscosity and low cost. However, linear ether electrolytes have the following problems: (1) Narrow liquid range. Linear ether solvents are usually easy to volatilize, which greatly restricts the operation of batteries in high temperature environments; (2) Poor antioxidant capacity. Since the lone pair electrons of oxygen atoms and hydrogen atoms on α-carbon in linear ether solvents are easily oxidized, they have poor oxidation stability and unstable positive electrode interface chemistry, and are therefore not suitable for high-voltage lithium metal batteries (above 4.3V).

[0004] In the prior art, CN118054085A discloses a battery electrolyte using a cyclic ether compound combined with a linear ether compound. The cyclic ether is a single-ring structure and does not have a branched structure, and must be used together with a linear ether to achieve good electrochemical stability for a lithium metal negative electrode. CN116315100A discloses an electrolyte formed by a cyclic ether with no branched structure, wherein the cyclic ether with no branched structure is a monocyclic diether or monocyclic triether compound and is used as a co-solvent of the electrolyte and must be used together with other linear ethers. However, the defect is that it only relies on regulating the number and position of oxygen atoms on the cyclic ether, and fails to achieve a stable electrochemical interface for a single cyclic ether solvent at both the lithium metal negative electrode and the sulfur positive electrode, which greatly limits the application of cyclic ether solvents in alkali metal battery systems.

[0005] CN113661589A discloses a method of using monocyclic diethers as electrolyte co-solvents and applying them to a lithium-ion secondary battery system with graphite as the negative electrode, but similarly fails to solve the problem of insufficient stability of the monocyclic diether co-solvent strategy in alkali metal negative electrodes. Obviously, it is very difficult to break through the application of cyclic ethers as the main solvent or the sole solvent of the electrolyte in the alkali metal battery system.

[0006] In view of the above problems, the present invention designs a cyclic ether electrolyte system suitable for alkali metal batteries. The electrolyte can be adapted to high-voltage positive electrode materials or sulfur positive electrodes at the same time, achieving a breakthrough in high voltage and high capacity of alkali metal batteries. Summary of the invention

[0007] In view of the above-mentioned problems, the object of the present invention is to provide an electrolyte based on cyclic ether solvents and suitable for alkali metal battery systems and a preparation method thereof through reasonable molecular design.

[0008] The present invention aims to design and synthesize cyclic ether solvents, and the main technical features are as follows: (1) by adjusting the number of carbon atoms and oxygen atoms in the cyclic alkyl group, the oxidation stability is improved; (2) on the basis of the cyclic structure, an ether branched structure is introduced and the number and ratio of carbon / oxygen atoms are regulated to regulate the interaction between the cyclic ether solvent and lithium ions, thereby improving the electrochemical stability of the electrolyte. In addition, the cyclic ether solvent can also inhibit the solubility of lithium polysulfide while retaining the high solubility of commonly used lithium / sodium salts. When a sulfur composite positive electrode is used, the positive / negative electrode can have both stable interface chemical characteristics and regulated conversion kinetics of polysulfide.

[0009] In particular, our molecular design concept emphasizes that at least one oxygen atom must be contained in both the ring structure and the branched structure. Surprisingly, this molecular design has excellent stability when used as a solvent in an electrolyte and is resistant to high voltages. This is a new discovery that has not been mentioned in previous studies.

[0010] One object of the present invention is to disclose an alkali metal battery cyclic ether electrolyte, which comprises a lithium salt, a sodium salt and a specific cyclic ether solvent;

[0011] The specific cyclic ether has a cyclic structure and contains a branch chain, and both the cyclic structure and the branch chain contain at least one oxygen atom.

[0012] Furthermore, the cyclic structure is selected from one or more of a four-membered ring, a five-membered ring, a six-membered ring or an eight-membered ring.

[0013] Furthermore, in the specific cyclic ether, the total number of oxygen atoms is 2-4.

[0014] Furthermore, the branched chain may be selected from one or more of a linear structure, a branched structure or a cyclic structure.

[0015] Further, the lithium salt is selected from one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, lithium bis(oxalato)borate, lithium difluorooxalatoborate, and lithium perchlorate;

[0016] The sodium salt is selected from one or more of sodium bis(trifluoromethanesulfonyl)imide, sodium hexafluorophosphate, sodium tetrafluoroborate, sodium hexafluoroarsenate, sodium trifluoromethanesulfonate, sodium dioxalatoborate, sodium difluorooxalatoborate, and sodium perchlorate.

[0017] Furthermore, the specific cyclic ether structure is selected from one or more of the following structures:

[0018]

[0019]

[0020] Another object of the present invention is to disclose a method for preparing the cyclic ether electrolyte for an alkali metal battery, which comprises the following steps:

[0021] S1. In an anhydrous and oxygen-free environment, sodium cyanide and alcohol molecules are mixed and reacted, and then iodoalkane is added dropwise in an ice bath to continue the reaction;

[0022] The alcohol molecules include 2-hydroxyoxetane, 3-methyl-2-hydroxyoxetane, 2-hydroxymethyloxetane, 2-(2'-hydroxyethyl)oxetane, 2-methyl-4-hydroxy-1,3-dioxetane, 2-hydroxymethyl-4-methyloxetane, 2-hydroxymethyl-1,3-dioxetane, 2-dihydroxymethyloxetane, 2-hydroxytetrahydrofuran, 5-methyl-2-hydroxytetrahydrofuran, tetrahydrofurfuryl alcohol, 5-methyl-tetrahydrofurfuryl alcohol, alcohol, 2-(2'-hydroxyethyl)oxolane, 2-(2'-hydroxyethyl)-5-methyloxolane, 3-hydroxytetrahydrofuran, 5-methyl-3-hydroxytetrahydrofuran, 2-dihydroxymethyltetrahydrofuran, 5-methyl-2-hydroxymethyl-1,3-dioxolane, 2-hydroxyhexyl-1,3-dioxolane, 2-(2'-hydroxyethyl)-1,3-dioxolane, 2-hydroxymethyl-4-methyl-1,3-dioxolane, 2-hydroxyoxolane oxane, 3-hydroxyoxane, 2-hydroxy-5-methyloxane, 2-hydroxymethyloxane, 3-hydroxymethyloxane, 2-(2'-hydroxyethyl)oxane, 6-methyl-2-(2'-hydroxyethyl)oxane, 6-methyl-3-hydroxy-1,4-dioxane, 2-(dihydroxymethyl)oxane, 5-methyl-2-hydroxy-1,3-dioxane, 2-(2'-hydroxyethyl)-1,3-dioxane, 5-hydroxy- One of 1,3-dioxane, 2-hydroxymethyl-1,3-dioxane, 2-hydroxymethyloxocane, 2-(2'-hydroxyethyl)oxocane, 7-methyl-2-hydroxymethyloxocane, 2-hydroxyoxocane, 3-hydroxymethyloxocane, 7-methyl-3-hydroxymethyloxocane, 2-hydroxy-1,3-dioxocane, 2-hydroxymethyl-1,3-dioxocane, 3-hydroxy-1,5-dioxocane, and 5-(dihydroxymethyl)oxocane;

[0023] The iodinated alkane is one of methyl iodide, ethyl iodide and propyl iodide;

[0024] The organic solvent is tetrahydrofuran.

[0025] S2, quenching the reaction with water and purifying to obtain a cyclic ether;

[0026] S3, compounding the cyclic ether with lithium salt and sodium salt to obtain the alkali metal battery cyclic ether electrolyte.

[0027] Taking five-membered cyclic ether molecules as an example, the specific reaction mechanism and synthesis steps are as follows:

[0028]

[0029] Furthermore, the configuration concentration of the alkali metal battery cyclic ether electrolyte is 0.1-5 mol / L.

[0030] Furthermore, the lithium salt or sodium salt needs to be vacuum dried at a high temperature of 60 to 150° C. before the electrolyte can be prepared.

[0031] Another object of the present invention is to disclose an alkali metal battery formed by the cyclic ether electrolyte of the alkali metal battery. The alkali metal comprises a positive electrode, a negative electrode, a separator and the cyclic ether electrolyte to form a closed alkali metal battery.

[0032] The beneficial effects of the present invention are as follows:

[0033] 1. The cyclic ether electrolyte suitable for alkali metal batteries of the present invention, through reasonable molecular design, obtains a battery electrolyte suitable for alkali metal negative electrode with good compatibility, which can match ion embedding type and conversion type positive electrode materials at the same time. In addition, the present invention specifically solves key problems such as the stability of alkali metal negative electrodes and the serious polysulfide shuttle effect in alkali metal batteries. The cyclic ether electrolyte exhibits good electrochemical stability of lithium metal, and can achieve excellent cycle stability in a 4.3V battery system, solving the current technical problem that linear ether solvents cannot operate due to solvent decomposition in a 4.3V battery system. In addition, the cyclic ether electrolyte has a higher capacity and capacity retention rate in the lithium-sulfur battery system, realizing the design of a new lithium-sulfur battery electrolyte. The above effects effectively expand the design and synthesis technology routes of cyclic ether electrolytes and the application scenarios of alkali metal batteries.

[0034] 2. The present invention is suitable for a cyclic ether electrolyte for alkali metal batteries, has a simple preparation process, and is easy to synthesize and apply on a large scale. Through reasonable structural design, the obtained electrolyte is helpful to promote the development of high energy density alkali metal batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The hydrogen nuclear magnetic resonance spectrum of compound 11 in Example 1 is shown.

[0036] Figure 2 The hydrogen nuclear magnetic resonance spectrum of compound 12 in Example 2 is shown.

[0037] Figure 3 The hydrogen nuclear magnetic resonance spectrum of compound 16 in Example 3 is shown.

[0038] Figure 4 The hydrogen nuclear magnetic resonance spectrum of compound 22 in Example 4 is shown.

[0039] Figure 5 The graph shows the electrochemical performance of Li||Cu batteries in different electrolytes.

[0040] Figure 6 The electrochemical performance diagram of Li||NCM811 battery in different electrolytes is shown.

[0041] Figure 7 The figure shows the electrochemical performance of Li||S batteries in different electrolytes.

[0042] Figure 8 The graph shows the electrochemical performance of Na||Cu battery in different electrolytes. DETAILED DESCRIPTION

[0043] The present invention is further described below by means of specific examples, the purpose of which is to help better understand the content of the present invention, specifically including the synthesis of compounds and device preparation methods, but these specific implementation schemes do not limit the protection scope of the present invention in any way. Unless otherwise stated, the raw materials, reactions and post-treatment methods appearing in the examples are all common raw materials on the market.

[0044] The practice of the present invention can adopt the conventional techniques of compound chemistry within the art. In the following examples, efforts are made to ensure the accuracy of the numbers used (including amounts, temperatures, reaction times, etc.), but some experimental errors and deviations should be considered. The temperatures used in the following examples are expressed in "°C" and the pressure is atmospheric pressure or near atmospheric pressure. The solvents used are purchased as analytical or chromatographically pure, and all reactions are carried out in a nitrogen atmosphere. Unless otherwise noted, all reagents are commercially available.

[0045] Example 1

[0046] A method for preparing a cyclic ether electrolyte for a lithium-sulfur battery is as follows:

[0047] S1. The synthetic route of the specific cyclic ether compound 11 is as follows:

[0048]

[0049] 3.6g of sodium hydride and 150mL of tetrahydrofuran were added to a 500mL three-necked round-bottom flask without water or oxygen. 10.22g of tetrahydrofurfuryl alcohol was added dropwise under an ice-water bath and stirring. After the addition was complete, the ice bath was removed and the mixture was reacted at room temperature for 2h. Subsequently, 21.29g of methyl iodide was added dropwise under an ice-water bath. After the addition was complete, the ice bath was removed and the mixture was heated to 70°C and reacted for 12h. After the reaction was completed and cooled to room temperature, water was added dropwise under stirring to quench the excess sodium hydride; after filtration, rotary evaporation, washing with saturated brine, drying with anhydrous sodium sulfate, filtration, and reduced pressure distillation, the final product molecule 2-(methoxymethyl)tetrahydrofuran, i.e., compound 11, was obtained. The obtained compound 11 was placed in a glove box at 25°C with a water content and an oxygen content of less than 0.01ppm, and dried over molecular sieves for three days and three nights to remove moisture.

[0050] S2. Preparation of cyclic ether electrolyte based on compound 11:

[0051] Lithium bis(trifluoromethane)sulfonyl imide (LiTFSI) and lithium nitrate (LiNO3) were placed in a vacuum dryer at 100°C for 12 h. In a glove box at 25°C with a water content and an oxygen content less than 0.01 ppm, LiTFSI and LiNO3 were weighed and dissolved in compound 11 and stirred for 12 h to obtain LiNO3 with a concentration of 0.2 mol L -1 The concentration of LiTFSI is 1 mol L -1 cyclic ether electrolyte (denoted as M11-1TFSI).

[0052] Example 2

[0053] A method for preparing a cyclic ether electrolyte for an alkali metal battery is as follows:

[0054] S1. The synthetic route of the specific cyclic ether compound 12 is as follows:

[0055]

[0056] 3.6 g of sodium hydride and 150 mL of tetrahydrofuran were added to a 500 mL three-necked round-bottom flask without water or oxygen. 10.22 g of tetrahydrofurfuryl alcohol was added dropwise under an ice-water bath and stirring. After the addition was complete, the ice bath was removed and the mixture was reacted at room temperature for 2 h. Subsequently, 23.40 g of ethyl iodide was added dropwise under an ice-water bath. After the addition was complete, the ice bath was removed and the mixture was heated to 70 ° C and reacted for 12 h. After the reaction was completed and cooled to room temperature, water was added dropwise under stirring to quench the excess sodium hydride; after filtration, rotary evaporation, washing with saturated brine, drying with anhydrous sodium sulfate, filtering, and reduced pressure distillation, the final product molecule 2-(ethoxymethyl)tetrahydrofuran, i.e., compound 12, was obtained. The obtained compound 12 was placed in a glove box at 25 ° C with a water content and an oxygen content of less than 0.01 ppm, and dried over molecular sieves for three days and three nights to remove moisture.

[0057] S2. Preparation of cyclic ether electrolyte solution based on compound 12:

[0058] S2-1. Lithium bis(fluorosulfonyl)imide (LiFSI) was placed in a vacuum dryer at 100°C for 12 h. In a glove box at 25°C with a water content and an oxygen content less than 0.01 ppm, LiFSI was weighed and dissolved in compound 12 and stirred for 12 h to obtain LiFSI with a concentration of 1 mol L -1 Cyclic ether electrolyte (denoted as M12-1FSI)

[0059] S2-2, LiTFSI and LiNO3 were placed in a vacuum dryer at 100°C for 12h; in a glove box at 25°C with a water content and an oxygen content of less than 0.01ppm, LiTFSI and LiNO3 were weighed and dissolved in compound 12 and stirred for 12h to obtain LiNO3 with a concentration of 0.2molL -1 The concentration of LiTFSI is 1 mol L -1 cyclic ether electrolyte (denoted as M12-1TFSI).

[0060] S2-3, sodium hexafluorophosphate (NaPF6) was placed in a vacuum dryer at 100°C for 12 hours; in a glove box at 25°C with a water content and an oxygen content less than 0.01 ppm, NaPF6 was weighed and dissolved in compound 12 and stirred for 12 hours to obtain NaPF6 with a concentration of 1 mol L -1 cyclic ether electrolyte (denoted as M12-1NaPF6).

[0061] Example 3

[0062] A method for preparing a cyclic ether electrolyte for an alkali metal battery is as follows:

[0063] S1. The synthetic route of the specific cyclic ether compound 16 is as follows:

[0064]

[0065] 3.6g of sodium hydride and 150mL of tetrahydrofuran were added to a 500mL three-necked round-bottom flask without water or oxygen. 10.22g of tetrahydrofurfuryl alcohol was added dropwise under an ice-water bath and stirring. After the addition was complete, the ice bath was removed and the mixture was reacted at room temperature for 2h. Subsequently, 25.50g of iodopropane was added dropwise under an ice-water bath. After the addition was complete, the ice bath was removed and the mixture was heated to 70°C and reacted for 12h. After the reaction was completed and cooled to room temperature, water was added dropwise under stirring to quench the excess sodium hydride; after filtration, rotary evaporation, washing with saturated brine, drying with anhydrous sodium sulfate, filtration, and reduced pressure distillation, the final product molecule 2-(propyloxymethyl)tetrahydrofuran, i.e., compound 16, was obtained. The obtained compound 16 was placed in a glove box at 25°C with a water content and an oxygen content of less than 0.01ppm, and dried over molecular sieves for three days and three nights to remove moisture.

[0066] S2. Preparation of cyclic ether electrolyte based on compound 16:

[0067] S2-1. Place LiFSI under vacuum drying at 100°C for 12 h. In a glove box at 25°C with a water content and an oxygen content less than 0.01 ppm, weigh LiFSI and dissolve it in compound 16 and stir for 12 h to obtain LiFSI with a concentration of 1 mol L -1 Cyclic ether electrolyte (denoted as M16-1FSI)

[0068] S2-2, LiTFSI and LiNO3 were placed in a vacuum dryer at 100°C for 12 h; in a glove box at 25°C with a water content and an oxygen content of less than 0.01 ppm, LiTFSI and LiNO3 were weighed and dissolved in compound 16 and stirred for 12 h to obtain LiNO3 with a concentration of 0.2 molL -1 The concentration of LiTFSI is 1 mol L -1 cyclic ether electrolyte (denoted as M16-1TFSI).

[0069] S2-3, NaPF6 was placed in a vacuum dryer at 100°C for 12 h; in a glove box at 25°C with a water content and an oxygen content less than 0.01 ppm, NaPF6 was weighed and dissolved in compound 16 and stirred for 12 h to obtain NaPF6 with a concentration of 1 mol L -1 cyclic ether electrolyte (denoted as M16-1NaPF6).

[0070] Example 4

[0071] A method for preparing a cyclic ether electrolyte for a lithium-sulfur battery is as follows:

[0072] S1. The synthetic route of the specific cyclic ether compound 22 is as follows:

[0073]

[0074] 3.6 g of sodium hydride and 150 mL of tetrahydrofuran were added to a 500 mL three-necked round-bottom flask without water or oxygen. 10.42 g of 1,3-dioxane-2-methanol was added dropwise under an ice-water bath and stirring. After the addition was complete, the ice bath was removed and the mixture was reacted at room temperature for 2 h. Subsequently, 21.29 g of methyl iodide was added dropwise under an ice-water bath. After the addition was complete, the ice bath was removed and the mixture was heated to 70 ° C for 12 h. After the reaction was completed and cooled to room temperature, water was added dropwise under stirring to quench the excess sodium hydride; after filtration, rotary evaporation, washing with saturated brine, drying with anhydrous sodium sulfate, filtration, and reduced pressure distillation, the final product molecule 2-(methoxymethyl)-1,3-dioxolane, i.e., compound 22, was obtained. The obtained compound 22 was placed in a glove box at 25 ° C with a water content and an oxygen content of less than 0.01 ppm, and dried over molecular sieves for three days and three nights to remove moisture.

[0075] S2. Preparation of cyclic ether electrolyte based on compound 22:

[0076] LiTFSI and LiNO3 were placed in a vacuum dryer at 100°C for 12 h. In a glove box at 25°C with a water content and an oxygen content less than 0.01 ppm, LiTFSI and LiNO3 were weighed and dissolved in compound 22 and stirred for 12 h to obtain a LiNO3 concentration of 0.2 mol / L -1 The concentration of LiTFSI is 1 mol L -1 cyclic ether electrolyte (denoted as M22-1TFSI).

[0077] Figure 1-4 The hydrogen NMR spectra of compounds 11, 12, 16 and 22 are shown respectively.

[0078] Comparative Example 1

[0079] LiFSI was placed in a vacuum dryer at 100 °C for 12 h. In a glove box at 25 °C with a water content and an oxygen content less than 0.01 ppm, LiFSI was weighed and dissolved in ethylene glycol dimethyl ether (DME) and stirred for 12 h to obtain a LiFSI concentration of 1 mol L -1 electrolyte (denoted as D-1FSI).

[0080] Comparative Example 2

[0081] LiTFSI and LiNO3 were placed in a vacuum dryer at 100°C for 12 h. LiTFSI was weighed and dissolved in a 1:1 volume ratio 1,3-dioxolane (DOL) / DME mixed solvent in a glove box at 25°C with a water content and an oxygen content of less than 0.01 ppm to prepare a LiNO3 solution with a concentration of 0.2 mol L -1 , LiTFSI concentration is 1 mol L -1 electrolyte (denoted as DD-1TFSI).

[0082] Comparative Example 3

[0083] NaPF6 was placed in a vacuum dryer at 100°C for 12 hours; in a glove box at 25°C with a water content and an oxygen content less than 0.01 ppm, NaPF6 was weighed and dissolved in DME and stirred for 12 hours to obtain a NaPF6 concentration of 1 mol L -1 electrolyte (denoted as D-1NaPF6).

[0084] Alkali metal battery test example

[0085] Li||Cu battery assembly: In a glove box at 25°C with water and oxygen values ​​both below 0.01 ppm, Li||Cu batteries were assembled using copper foil as the positive electrode, lithium sheet as the negative electrode, and D-1FSI of Comparative Example 1 or M12-1FSI of Example 2 as the electrolyte.

[0086] Li||NCM811 battery assembly: NCM811, acetylene black, and PVDF binder are added to N-methylpyrrolidone (NMP) in a certain mass ratio to prepare a slurry; the slurry is evenly coated on an aluminum foil using a doctor blade technique, and then transferred to a 120°C oven for drying, and cut into electrode sheets of a specific size using a slicer, and stored in a glove box; in a glove box at a temperature of 25°C, with water and oxygen values ​​both lower than 0.01ppm, a Li||NCM811 battery is assembled using an NCM811 electrode sheet as the positive electrode, lithium metal as the negative electrode, and D-1FSI of Comparative Example 1 or M12-1FSI of Example 2 as the electrolyte.

[0087] Li||S battery assembly: add deionized water to prepare a slurry according to a certain mass ratio of carbon nanotube / sulfur composite powder, acetylene black and LA133; use a doctor blade coating technique to evenly coat the slurry on a carbon-coated aluminum foil, vacuum dry it at 60°C for 24 hours, and use a slicer to cut it into electrode sheets of a specific size (referred to as CNT / S electrode sheets), and store them in a glove box; in a glove box at a temperature of 25°C, with water and oxygen values ​​both lower than 0.01ppm, use the CNT / S electrode sheet as the positive electrode, lithium metal as the negative electrode, and use DD-1TFSI of Comparative Example 2, M11-1TFSI of Example 1, and M22-1TFSI of Example 3 as electrolytes to assemble a Li||S battery.

[0088] Na||Cu battery assembly: In a glove box at 25°C with water and oxygen values ​​both below 0.01 ppm, a Na||Cu battery was assembled using copper foil as the positive electrode, a sodium sheet as the negative electrode, and D-1NaPF6 of Comparative Example 3 or M12-1NaPF6 of Example 2 as the electrolyte.

[0089] The electrochemical performance of the battery obtained in the preparation example was tested. The test results are as follows:

[0090] (1) The electrolytes of Example 2 and Comparative Example 1 were used to assemble Li||Cu batteries and the temperature was 25°C and the current density was 1 mA cm -2 , specific capacity is 1 mAh cm -2 Under the same conditions, the Coulomb efficiency was tested.

[0091] Figure 5 The graph shows the electrochemical performance of Li||Cu battery in different electrolytes at 25°C.

[0092] from Figure 5 It can be seen that at a current density of 1 mA cm -2 , specific capacity is 1 mAh cm -2Under the test conditions, the average coulombic efficiency of M12-1FSI in Example 2 reached 98.7%, while the average coulombic efficiency of D-1FSI in Comparative Example 1 was 97.5%, indicating that the M12-1FSI electrolyte in Example 2 has good compatibility with the lithium metal negative electrode and reversibility of lithium deposition and stripping.

[0093] (2) The electrolytes of Example 2 and Comparative Example 1 were used to assemble Li||NCM811 batteries and the electrochemical cycle stability was tested at a voltage of 4.3 V and a current density of 1 C.

[0094] Figure 6 The electrochemical performance diagram of Li||NCM811 battery in different electrolytes at a voltage of 4.3V and a rate of 1C is shown.

[0095] from Figure 6 As can be seen from Table 1, the Li||NCM811 battery using the D-1FSI electrolyte of Comparative Example 1 fails quickly after 185 cycles, while the Li||NCM811 battery using the M12-1FSI electrolyte of Example 2 can still maintain a specific capacity of 148.2 mAh g after 300 cycles. – 1 The capacity retention rate is as high as 81.1%, and the average Coulombic efficiency reaches 99.5%, showing excellent cycle stability.

[0096] Table 1 Cycling performance of Li||NCM811 battery in different electrolytes at 4.3V and 1C

[0097]

[0098]

[0099] (3) The electrolytes of Example 1, Example 4 and Comparative Example 2 were used to assemble Li||S batteries and perform electrochemical cycle stability tests.

[0100] Figure 7 The graph shows the electrochemical performance of Li||S batteries in different electrolytes.

[0101] from Figure 7 As can be seen from Table 2, at a current density of 0.1C, using the M11-1TFSI electrolyte in Example 1, the initial discharge capacity of the Li||S battery reaches 1199.3 mAh g -1 After 90 cycles, the capacity is 747.2 mAh g -1 Using the M22-1TFSI electrolyte in Example 3, the initial discharge capacity of the Li||S battery reached 1023.5mAh g -1After 90 cycles, the capacity is 704.2 mAh g -1 ; Using the DD-1TFSI electrolyte in Comparative Example 2, the initial discharge capacity of the Li||S battery is only 884.6 mAhg -1 After 90 cycles, the capacity is 510.0 mAh g -1 , lower than the two electrolytes in Examples 1 and 3.

[0102] Table 2 Cycling performance of Li||S batteries in different electrolytes

[0103]

[0104] (4) The electrolytes of Example 2 and Comparative Example 3 were used to assemble a Na||Cu battery and the temperature was 25°C and the current density was 1 mA cm -2 , specific capacity is 1 mAh cm -2 Under the same conditions, the Coulomb efficiency was tested.

[0105] Figure 8 The graph shows the electrochemical performance of Na||Cu battery in different electrolytes at 25°C.

[0106] from Figure 8 It can be seen that at a current density of 1 mA cm -2 , specific capacity is 1 mAh cm -2 Under the test conditions, the average coulombic efficiency of the M12-1NaPF6 electrolyte in Example 2 reaches 99.8% and can stably operate for more than 500 cycles, while the D-1NaPF6 electrolyte in Comparative Example 3 can only operate for 43 cycles, indicating that the M12-1NaPF6 electrolyte in Example 2 has good compatibility with the sodium metal negative electrode and reversibility of sodium deposition and stripping.

[0107] Table 3 Cycling performance of Na||Cu batteries in different electrolytes at 25℃

[0108]

[0109] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

[0110] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A cyclic ether electrolyte for an alkali metal battery, characterized in that: The cyclic ether electrolyte for alkali metal batteries includes lithium salt, sodium salt and a specific cyclic ether solvent; The specific cyclic ether has a cyclic structure and contains a branch chain, and both the cyclic structure and the branch chain contain at least one oxygen atom.

2. The cyclic ether electrolyte for alkali metal batteries according to claim 1, characterized in that: The cyclic structure is selected from one or more of a four-membered ring, a five-membered ring, a six-membered ring or an eight-membered ring.

3. The cyclic ether electrolyte for alkali metal batteries according to claim 1, characterized in that: In the specific cyclic ether, the total number of oxygen atoms is 2-4.

4. The cyclic ether electrolyte for alkali metal batteries according to claim 1, characterized in that: The branched chain may be selected from one or more of a linear structure, a branched structure or a cyclic structure.

5. The cyclic ether electrolyte for alkali metal batteries according to claim 1, characterized in that: The lithium salt is selected from one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, lithium bis(oxalato)borate, lithium difluorooxalatoborate, and lithium perchlorate; The sodium salt is selected from one or more of sodium bis(trifluoromethanesulfonyl)imide, sodium hexafluorophosphate, sodium tetrafluoroborate, sodium hexafluoroarsenate, sodium trifluoromethanesulfonate, sodium dioxalatoborate, sodium difluorooxalatoborate, and sodium perchlorate.

6. The cyclic ether electrolyte for alkali metal batteries according to claim 1, characterized in that: The specific cyclic ether structure is selected from one or more of the following structures: 。 7. The method for preparing the cyclic ether electrolyte for alkali metal batteries according to any one of claims 1 to 6, characterized in that: The steps include: S1. In an anhydrous and oxygen-free environment, sodium cyanide and alcohol molecules are mixed and reacted, and then iodoalkane is added dropwise in an ice bath to continue the reaction; S2, quenching the reaction with water and purifying to obtain a cyclic ether; S3, compounding the cyclic ether with lithium salt and sodium salt to obtain the alkali metal battery cyclic ether electrolyte.

8. The method for preparing the cyclic ether electrolyte for alkali metal batteries according to claim 7, characterized in that: The configuration concentration of the alkali metal battery cyclic ether electrolyte is 0.1-5 mol / L.

9. The method for preparing the cyclic ether electrolyte for alkali metal batteries according to claim 7, characterized in that: The lithium salt or sodium salt needs to be vacuum dried at a high temperature of 60 to 150° C. before the electrolyte can be prepared.

10. An alkali metal battery formed by the alkali metal battery cyclic ether electrolyte according to any one of claims 1 to 6.

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