Alkali metal secondary battery electrolyte easy to store at normal temperature and battery containing electrolyte

Abstract

The invention discloses an alkali metal secondary battery electrolyte easy to store at normal temperature and a battery containing the electrolyte, the electrolyte comprises a main salt, a non-aqueous solvent and an additive composition, the main salt is selected from a main lithium salt or a main sodium salt; the additive composition comprises a silyl dicarboxylate compound which is used as a first additive and at least comprises a structure shown in (I) and a compound which is used as a second additive and has a structure shown in (II-A), (II-B) or (II-C), and the specific structure is shown in the specification. The electrolyte prepared from the additive composition disclosed by the invention can be used for inhibiting a polymerization reaction caused by attacking solvent molecules such as ethylene carbonate (EC) and methyl ethyl carbonate (EMC) by a byproduct PF5 generated after the reaction of a silane-based dicarboxylate compound and Li / NaPF6; and meanwhile, the effective effect generated by the main reaction of the silyl dicarboxylate compound and Li / NaPF6 in the electrolyte is not influenced, the problem of color change after the electrolyte is stored can be solved, and meanwhile, the high-temperature storage and cycle performance of the battery is improved.

Description

Technical Field

[0001] This invention relates to the field of electrolytes, and in particular to an alkali metal secondary battery electrolyte that is easy to store at room temperature and its application in alkali metal secondary batteries. Background Technology

[0002] With the continuous development of technology, alkali metal secondary batteries have been widely used as a power source in electric vehicles, consumer batteries, and energy storage in recent years. Alkali metal secondary batteries have advantages such as high energy density, long lifespan, and lightweight, and therefore have been widely applied in mobile devices, electric vehicles, and energy storage systems.

[0003] In practical use, factors such as the heat generated by the equipment itself during long-term operation and the rise in ambient temperature cause alkali metal secondary batteries to face high-temperature conditions. As the temperature increases, the reactivity of the electrodes and electrolytes increases, and the side reactions intensify, leading to serious deterioration of battery performance. Therefore, effective technologies are needed to improve the high-temperature stability of the battery.

[0004] Patent 202311200867.7 proposes using a silane-containing dicarboxylic acid ester compound as a non-aqueous electrolyte for secondary batteries, which can effectively improve the high-temperature cycle performance of high-voltage batteries above 4.3V, but is detrimental to high-temperature storage performance. Patent KR100695109A discloses silane-containing dicarboxylic acid ester compounds, which can improve the 1C charge-discharge rate cycle life at room temperature and suppress the increase in battery thickness during cycling, but this patent does not mention its potential defects in high-temperature storage under high-voltage systems.

[0005] Through experimental research, the applicant discovered that electrolytes containing silanedicarboxylic acid esters exhibit discoloration during long-term storage. This discoloration is presumably attributed to the attack of PF5, a byproduct of the reaction between the silanedicarboxylic acid ester and Li / NaPF6, on solvent molecules such as ethylene carbonate (EC) and ethyl methyl carbonate (EMC), leading to polymerization and the formation of polymers containing conjugated double bonds, thus causing electrolyte discoloration. Simultaneously, the color problem caused by these side reactions is accompanied by a deterioration in the battery's electrochemical performance, such as a decrease in high-temperature storage performance. Therefore, an electrolyte stabilizer is needed to suppress this side reaction process without affecting the effective function of the silanedicarboxylic acid ester compound in the electrolyte (its primary reaction with Li / NaPF6). Summary of the Invention

[0006] One objective of this invention is to overcome the shortcomings of the prior art and provide an electrolyte solution comprising first and second additives. This electrolyte solution can suppress the polymerization reaction initiated by the byproduct PF5 from the reaction of silane dicarboxylic acid ester compounds with Li / NaPF6, which attacks solvent molecules such as ethylene carbonate (EC) and ethyl methyl carbonate (EMC), thus solving the problem of electrolyte discoloration after storage and improving the battery's high-temperature storage and high-temperature cycling performance.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] An alkali metal secondary battery electrolyte that is easy to store at room temperature, the electrolyte comprising a main salt, a non-aqueous solvent, and an additive composition, wherein the additive composition comprises at least:

[0009] The first additive is selected from silyl dicarboxylic acid ester compounds of formula (I):

[0010]

[0011] In formula (I), R1, R2, R3, R4, R5, R6, R7, and R8 are independently selected from hydrogen, fluorine, C1-C6 alkyl, C1-C6 fluoroalkyl, C1-C6 alkoxy, or C1-C6 fluoroalkoxy; n is an integer from 0 to 4, and R7 and R8 in each repeating unit are selected from the same or different substituents;

[0012] Preferably, in formula (I), R1, R2, R3, R4, R5, R6, R7, and R8 are independently selected from hydrogen, fluorine, C1-C4 alkyl, C1-C4 fluoroalkyl, C1-C4 alkoxy, or C1-C4 fluoroalkoxy; and n is selected from 0, 1, or 2.

[0013] More preferably, in formula (I), R1, R2, R3, R4, R5, and R6 are independently selected from methyl, ethyl, isopropyl, tert-butyl, or fluoromethyl; and R7 and R8 are independently selected from hydrogen, fluorine, methyl, or fluoromethyl.

[0014] More preferably, the first additive is selected from at least one of the compounds shown in the following structures:

[0015]

[0016]

[0017] The second additive is selected from compounds with the structure shown in formula (II-A), (II-B) or (II-C):

[0018]

[0019] In formula (II-A), R9, R 10 R 11 It may be independently selected from at least one alkyl or aryl group of C1-C12;

[0020] Preferably, in formula (II-A), R9, R 10 R 11 Independently selected from C1-C6 alkyl or aryl groups;

[0021] In equation (II-B), R 12 The group is selected from C1-C20 alkyl, C1-C20 substituted alkyl, substituted phenyl, and substituted biphenyl, wherein the alkyl group is a chain alkyl or cycloalkyl, and the substituent is hydrogen, halogen, C1-C20 alkyl, phosphate ester group, sulfonyl group, or thio group; the halogen is selected from fluorine, chlorine, bromine, and iodine;

[0022] 0≤x≤1, 0≤y≤1, 0≤z≤1.

[0023] Preferably, R 12 It is selected from C1-C10 alkyl, C1-C10 substituted alkyl, wherein the substituent is hydrogen, halogen, or C1-C10 alkyl.

[0024] In formula (II-C), R 13 R 14 R 15 It is independently selected from C1-C6 alkyl, C1-C6 fluoroalkyl, C3-C6 cycloalkyl, C2-C6 alkenyl, C2-C6 alkynyl or cyanoalkyl;

[0025] Preferably, in formula (II-C), R 13 R 14 R 15 It is independently selected from C1-C3 alkyl, C1-C3 fluoroalkyl, C3-C5 cycloalkyl, C2-C3 alkenyl, C2-C3 alkynyl or cyanoalkyl.

[0026] More preferably, the second additive is selected from at least one of the following structures:

[0027]

[0028] The first additive accounts for 0.01 to 5.0 wt% of the total mass of the electrolyte;

[0029] The second additive accounts for 0.005 to 0.1 wt% of the total mass of the electrolyte.

[0030] Preferably, the first additive accounts for 0.1 to 3.0 wt% of the total mass of the electrolyte, more preferably 0.5 to 2.0 wt%.

[0031] Preferably, the second additive accounts for 0.01 to 0.05 wt% of the total mass of the electrolyte, more preferably 0.02 to 0.03 wt%.

[0032] The main salt is selected from either the main lithium salt LiPF6 or the main sodium salt NaPF6, and the concentration of the main lithium salt or the main sodium salt in the electrolyte is 0.4 to 3 M.

[0033] The first additive and main salt of this invention can react during storage to generate a new additive. This additive is generated in situ, and electrochemical performance tests have shown that it can further improve the high-temperature cycle performance of the battery under high-voltage fast charging conditions. However, the applicant has found through experimental research that electrolytes containing silane dicarboxylic acid ester compounds exhibit discoloration during long-term storage. It is speculated that this discoloration is due to the byproduct PF5 from the reaction of silane dicarboxylic acid ester compounds with Li / NaPF6 attacking solvent molecules such as EC and EMC, leading to polymerization reactions that produce polymers containing conjugated double bonds, resulting in electrolyte discoloration. At the same time, the color problem caused by electrolyte side reactions is also accompanied by the deterioration of battery electrochemical performance, such as a decrease in high-temperature storage performance.

[0034] The second additive of this invention contains reducing and weakly basic groups, which can react with PF5, a byproduct of the reaction between silane dicarboxylic acid ester compound and Li / NaPF6. This prevents PF5 from attacking solvent molecules such as EC and EMC, thus preventing polymerization reactions that produce polymers containing conjugated double bonds, which would cause discoloration of the electrolyte and improve its stability. At the same time, the second additive itself has the ability to annihilate oxidizing components generated by the positive electrode, thereby improving the electrochemical performance of the battery under high voltage and high temperature.

[0035] The remaining organic solvents used in this invention can be common solvents found in electrolytes. Preferably, the organic solvents are selected from at least one of C3-C6 carbonates or fluorocarbonates, C3-C8 carboxylic acids, sulfones, and ethers. More preferably, the C3-C6 carbonate or fluorocarbonate compound is selected from at least one of ethylene carbonate, propylene carbonate, butene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, fluoroethylene carbonate, and difluoroethylene carbonate; the C3-C8 carboxylic acid ester compound is selected from at least one of γ-butyrolactone, methyl acetate, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, ethyl butyrate, propyl acetate, and propyl propionate; the sulfone compound is selected from at least one of sulfolane, dimethyl sulfoxide, dimethyl sulfone, and diethyl sulfone; and the ether compound is selected from at least one of triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

[0036] In order to further improve the battery performance, the lithium-ion battery electrolyte may further include a basic additive selected from at least one of fluoroethylene carbonate, vinylene carbonate, ethylene sulfate, tris(trimethylsilyl) phosphate, 1,3-propylene sultone, lithium difluorophosphate, lithium bis(fluorosulfonyl)imide, succinic anhydride, adiponitrile, cyclohexylbenzene, lithium bis(oxalato)difluorophosphate, lithium difluorooxalate borate, sodium difluorooxalate borate, sodium difluorophosphate, sodium bis(fluorosulfonyl)imide, and sodium bis(oxalato)difluorophosphate, and the mass percentage of any one of the basic additives in the total mass of the electrolyte is 0.1-5.0 wt%.

[0037] In a specific embodiment, the basic additives are vinylene carbonate with a mass fraction of 0.1-2.0 wt% and lithium difluorooxalate borate with a mass fraction of 0.1-2.0 wt%. By the combined use of vinylene carbonate, lithium difluorooxalate borate, the first additive and the second additive, on the basis of improving the storage stability of the electrolyte and the high-temperature performance of the battery, the cycle stability of the battery is further improved.

[0038] In a specific embodiment, the basic additives are a combination of vinylene carbonate with a mass fraction of 0.1-2.0 wt%, ethylene sulfate with a mass fraction of 0.1-3.0%, and lithium difluorophosphate with a mass fraction of 0.1-1.0%, which can further optimize the components of the positive and negative electrode-electrolyte interface film and improve the fast charge cycle performance of the battery.

[0039] The present invention also provides a battery, including a positive electrode, a negative electrode and a separator, and the battery includes the electrolyte described in any one of the above. When the battery is a lithium-ion battery, the active material of the positive electrode is selected from nickel-cobalt-manganese ternary materials, nickel-cobalt-aluminum ternary materials, lithium cobaltate materials or lithium iron phosphate materials, and the active material of the negative electrode is selected from graphite, silicon-carbon, silicon monoxide, silicon, tin, metallic lithium or their composite materials;

[0040] When the battery is a sodium-ion battery, the active material of the positive electrode is selected from at least one of NaMn (1-x-y) Ni y M x O2 (0≤x, y≤1, M is Cu, Fe, Co, sodium manganate, sodium vanadium phosphate, sodium fluoro vanadium phosphate, sodium iron phosphate, sodium manganese phosphate, sodium iron sulfate, Na x MnFe(CN)6 (0<x≤2), and the active material of the negative electrode is selected from at least one of hard carbon, carbon black, amorphous carbon, graphite, SnS2, Na2Ti3O7, silicon-based materials, metal oxides, metal sulfides or metallic sodium.

[0041] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0042] Through the synergistic effect of the first and second additives of this invention, the second additive can significantly improve the stability of the first additive and enhance the electrochemical performance of the battery under high voltage and high temperature. Specifically, by using an electrolyte solution containing the first and second additives, this electrolyte solution can suppress the polymerization reaction initiated by the byproduct PF5 of the reaction between silane dicarboxylic acid ester compound and Li / NaPF6 attacking solvent molecules such as EC and EMC, thus solving the problem of electrolyte discoloration after storage, and improving the battery's high-temperature storage and high-temperature cycling performance. Detailed Implementation

[0043] The present invention will be further described below with reference to specific embodiments, but the invention is not limited to these specific embodiments. Those skilled in the art should recognize that the present invention covers all alternatives, improvements, and equivalents that may be included within the scope of the claims.

[0044] The electrolyte formulation proposed in this invention is particularly suitable for high-voltage lithium-ion battery systems using ternary lithium nickel cobalt manganese oxide as the cathode, especially in maintaining the stability of the battery system when using Ni7 cathode material. In other words, the electrolyte formulation of this invention exhibits its advantages under the high-voltage conditions of ternary lithium-ion batteries. Therefore, this invention's embodiments, based on the basic electrolyte formulation for ternary lithium-ion battery systems, involve the preparation of the electrolyte, the fabrication of the battery, and the testing of its electrochemical performance.

[0045] I. Preparation of Electrolyte

[0046] Preparation of basic electrolyte 1: In an argon-filled glove box (moisture content < 5 ppm, oxygen content < 10 ppm), ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a mass ratio of 3:5:2 to form an organic solvent. Lithium hexafluorophosphate (LiPF6) is added until the concentration of lithium hexafluorophosphate based on the total electrolyte volume is 1M, thus obtaining basic electrolyte 1.

[0047] According to the data in the table below, quantitatively add the first and second additives to the basic electrolyte 1, and mix thoroughly to form the electrolyte:

[0048] Table 1 Electrolyte Formulation 1

[0049]

[0050]

[0051] To further improve the electrochemical performance of the battery, according to the electrolyte formulation in Table 2 below, based on the basic electrolyte 1, the following additives were added: first additive, second additive, 0.2% by mass of vinylene carbonate (VC), and 1% by mass of vinyl sulfate (DTD). Then, lithium difluorophosphate (LiDFP), lithium bis(fluorosulfonyl)imide (LiFSI), and fluoroethylene carbonate (FEC) were further added and mixed thoroughly to form the electrolyte.

[0052] Table 2 Electrolyte Formulation 2

[0053]

[0054] Note: After adjusting the amount of additives, only the amount of solvent in the base electrolyte is adjusted, and the distribution ratio of each component in the solvent remains unchanged.

[0055] II. Electrolyte Storage Colorimetric Test

[0056] A portion of the prepared electrolytes from the examples and comparative examples was transferred to sealed aluminum bottles and stored in a 50°C constant temperature oven. Samples were taken in a glove box before storage, after 7 days of storage, and after 28 days of storage to test the colorimetric values ​​of the electrolytes. The colorimetric method used was the platinum-cobalt colorimetric method, and the unit of colorimetry was Hazen. The test results are shown in Table 2 below.

[0057] Table 2. Electrolyte Colorimetry Test Results

[0058]

[0059] As shown in Table 2 above, the use of the first additive leads to an increase in the color of the electrolyte after storage, while the second additive has a significant effect on reducing the color of the electrolyte after storage.

[0060] II. Battery Manufacturing and Performance Testing

[0061] The lithium-ion battery electrolytes of the above embodiments and comparative examples were respectively used to make soft-pack lithium-ion power batteries with a capacity of 1000mAh. The lithium-ion power battery includes a positive electrode, a negative electrode, a separator, an electrolyte, and battery auxiliary materials. The positive electrode active material is lithium nickel cobalt manganese oxide, and the negative electrode active material is graphite.

[0062] The preparation process is as follows: the positive electrode, separator and negative electrode are wound together into a core, sealed with aluminum-plastic film and then baked to ensure that the electrode moisture meets the requirements. After baking, the cell is injected with electrolyte and then subjected to processes such as standing, formation, aging and capacity testing to obtain the finished soft-pack cell.

[0063] The performance of the aforementioned lithium-ion batteries was tested, including:

[0064] ① High-temperature storage performance test

[0065] At room temperature (25℃), the battery was charged at a constant current of 1C to the charging cutoff voltage (4.4V), and then charged at a constant voltage until the current dropped to 0.05C. It was then placed in a 60℃ oven for 56 days. After storage, the battery was cooled to room temperature, and the initial volume V1 and the volume V2 after storage were recorded. The battery was then discharged at a constant current of 1C to the cutoff voltage (2.8V), and the initial discharge capacity C1 and the discharge capacity C2 after storage were recorded. The high-temperature storage volume expansion rate and capacity retention rate were calculated using the following formula:

[0066] High-temperature storage volume expansion rate = (V2 / V1-1)*100%

[0067] High-temperature storage capacity retention rate = C2 / C1 * 100%

[0068] ② High-temperature cycling performance test

[0069] Charge the battery at a constant current of 1C at 45℃ until the charging cutoff voltage (4.4V), then charge at a constant voltage until the current drops to 0.1C, and then discharge at a constant current of 1C until the cutoff voltage (2.8V). Repeat this cycle for a specific number of cycles, recording the discharge capacity C3 of the first cycle and the discharge capacity C4 of the last cycle. Calculate the battery's capacity retention rate using the following formula:

[0070] High-temperature cycling capacity retention = C4 / C3 * 100%

[0071] The specific test results are shown in Table 3 below:

[0072] Table 3 Electrochemical test results for Ni7 / / AG from 2.8 to 4.4 V

[0073]

[0074]

[0075] Table 4 Electrochemical test results for Ni7 / / AG from 2.8 to 4.4 V

[0076]

[0077] Comparing Comparative Examples 1, 2, and 3, it can be seen that using the first additive alone can improve the high-temperature cycling performance, but it will increase the color of the electrolyte after storage and degrade the high-temperature storage performance; using the second additive alone can significantly reduce the color of the electrolyte after storage and improve the high-temperature storage performance, but it has no significant improvement on the high-temperature cycling performance.

[0078] Comparing Example 4, Comparative Example 2, and Comparative Example 3, it can be seen that the addition of the first additive can significantly improve the high-temperature cycle performance of the battery. The addition of the second additive can significantly reduce the electrolyte discoloration problem caused by the polymerization reaction triggered by the byproduct PF5 after the reaction of the first additive with LiPF6 attacking solvent molecules such as EC and EMC, thereby improving the high-temperature storage performance. At the same time, the synergistic effect of the first and second additives can be brought into play to further improve the high-temperature storage and high-temperature cycle performance.

[0079] Comparative Examples 1-9 and Comparative Examples 4-5 show that as the amount of the first additive I-1 increases, the high-temperature storage and high-temperature cycling performance first improves. However, as the amount of additive increases further, the color of the electrolyte and the battery performance deteriorate after storage. The optimal amount of additive is around 0.5-2.0 wt%.

[0080] Comparative Examples 4, 16-20, and 6-7 show that as the amount of the second additive II-1 increases, the high-temperature storage performance first improves. However, as the amount of additive increases further, the electrolyte color cannot be improved further, and the battery's high-temperature storage capacity retention and high-temperature cycling performance deteriorate. The optimal addition amount is approximately 0.02-0.03 wt%.

[0081] Comparing Examples 4, 10, 11, 12, and 13, it can be seen that compounds I-1, I-2, I-3, I-4, and I-5 all have the functions of the additives they represent and can be used interchangeably; comparing Examples 4, 14, and 15, compounds II-1, II-2, and II-3 all have the functions of the additives they represent and can be used interchangeably.

[0082] As can be seen from Tables 3-4 above, comparing Examples 4 and Examples 21-24, it can be seen that the first and second additives, when used in combination with vinyl sulfate, vinylene carbonate, lithium difluorophosphate, lithium bis(fluorosulfonyl)imide, and fluoroethylene carbonate, can further improve the battery's high-temperature storage and high-temperature cycling performance.

Claims

1. An alkali metal secondary battery electrolyte that is easy to store at room temperature, said electrolyte comprising a main salt, a non-aqueous solvent, and an additive composition, characterized in that: The additive composition comprises at least: The first additive has the following structure as shown in formula (I): In formula (I), R1, R2, R3, R4, R5, R6, R7, and R8 are independently selected from hydrogen, fluorine, C1-C6 alkyl, C1-C6 fluoroalkyl, C1-C6 alkoxy, or C1-C6 fluoroalkoxy; n is an integer from 0 to 4, and R7 and R8 in each repeating unit are selected from the same or different substituents; The second additive is selected from at least one compound with the structure shown in formula (II-A), (II-B) or (II-C): In formula (II-A), R9, R10, and R11 can be independently selected from C1-C12 alkyl or aryl groups; In formula (II-B), R12 is selected from C1-C20 alkyl, C1-C20 substituted alkyl, substituted phenyl, substituted biphenyl, wherein the alkyl group is a chain alkyl or cycloalkyl, and the substituent is hydrogen, halogen, C1-C20 alkyl, phosphate ester group, sulfonyl group, thio group; wherein the halogen is selected from fluorine, chlorine, bromine and iodine; 0≤x≤1, 0≤y≤1, 0≤z≤1. In formula (II-C), R13, R14, and R15 are independently selected from C1-C6 alkyl, C1-C6 fluoroalkyl, C3-C6 cycloalkyl, C2-C6 alkenyl, C2-C6 alkynyl, or cyanoalkyl. The first additive and the second additive account for a% and b% of the total mass of the electrolyte, respectively, and conform to the following relationship: 0.01≤a≤5.0； 0.005≤b≤0.1。 2. The alkali metal secondary battery electrolyte that is easy to store at room temperature according to claim 1, characterized in that: The amounts of the first additive and the second additive satisfy the following relationship: 0.1≤a≤3.0； 0.01≤b≤0.05。 3. The alkali metal secondary battery electrolyte that is easy to store at room temperature according to claim 1, characterized in that: In the first additive formula (I), R1, R2, R3, R4, R5, and R6 are independently selected from methyl, ethyl, isopropyl, tert-butyl, or fluoromethyl; R7 and R8 are independently selected from hydrogen, fluorine, methyl, or fluoromethyl.

4. The alkali metal secondary battery electrolyte that is easy to store at room temperature according to claim 1, characterized in that: In the second additive (II-A), R9, R10, and R11 are independently selected from C1-C6 alkyl or aryl groups; in the second additive (II-B), R12 is selected from C1-C10 alkyl, C1-C10 substituted alkyl, wherein the substituent is hydrogen, halogen, or C1-C10 alkyl; in the second additive (II-C), R... 13 R 14 R 15 It is independently selected from C1-C3 alkyl, C1-C3 fluoroalkyl, C3-C5 cycloalkyl, C2-C3 alkenyl, C2-C3 alkynyl or cyanoalkyl.

5. The alkali metal secondary battery electrolyte that is easy to store at room temperature according to claim 1, characterized in that: The first additive is selected from at least one of the compounds shown in the following structures:

6. The alkali metal secondary battery electrolyte that is easy to store at room temperature according to claim 1, characterized in that: The second additive is selected from at least one of the following structures:

7. The alkali metal secondary battery electrolyte that is easy to store at room temperature according to any one of claims 1-6, characterized in that: The additive composition further includes: The basic additive is selected from at least one of fluoroethylene carbonate, vinylene carbonate, ethylene sulfate, tris(trimethylsilyl)phosphate, 1,3-propenesulfonyl lactone, lithium difluorophosphate, lithium difluorosulfonylimide, succinic anhydride, adiponitrile, cyclohexylbenzene, lithium difluorophosphate bis(oxalate), lithium difluorooxalate borate, sodium difluorooxalate borate, sodium difluorophosphate, sodium difluorosulfonylimide, and sodium difluorophosphate bis(oxalate), and any one of the basic additives accounts for 0.1 to 5.0 wt% of the total mass of the electrolyte, and the basic additive is different from the main salt.

8. The alkali metal secondary battery electrolyte that is easy to store at room temperature according to any one of claims 1-7, characterized in that: The main salt is selected from lithium salt or sodium salt. The main lithium salt is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium bis(oxalate)borate, lithium difluorooxalateborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluorooxalate phosphate, lithium tri(oxalate) phosphate, or lithium difluorobis(oxalate) phosphate. The main sodium salt is selected from at least one of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium perchlorate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, or sodium difluorophosphate. The concentration of the main lithium salt or sodium salt in the electrolyte is 0.1–3 M. The non-aqueous solvent is selected from at least one of C3-C6 carbonate or fluorocarbonate compounds, C3-C8 carboxylic acid esters or fluorocarboxylic acid ester compounds, sulfone compounds or ether compounds; The C3-C6 carbonate or fluorocarbonate compound is selected from at least one of ethylene carbonate, propylene carbonate, butene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, or ethyl propyl carbonate; the C3-C8 carboxylic acid ester or fluorocarboxylic acid ester compound is selected from at least one of γ-butyrolactone, methyl acetate, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, ethyl butyrate, propyl acetate, or propyl propionate; the sulfone compound is selected from at least one of sulfolane, dimethyl sulfoxide, dimethyl sulfone, or diethyl sulfone; the ether compound is selected from at least one of triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol dimethyl ether, or dioxolane.

9. An alkali metal secondary battery, comprising a positive electrode, a separator, and a negative electrode, characterized in that: The alkali metal secondary battery is further filled with the alkali metal secondary battery electrolyte as described in any one of claims 1-8, which is easy to store at room temperature.

10. The alkali metal secondary battery according to claim 9, characterized in that: When the alkali metal secondary battery is a lithium-ion secondary battery, the active material of the positive electrode is selected from nickel-cobalt-manganese ternary materials, nickel-cobalt-aluminum ternary materials, lithium cobalt oxide materials or lithium iron phosphate materials, and the active material of the negative electrode is selected from graphite, silicon carbide, silicon suboxide, silicon, tin, metallic lithium or their composite materials. When the alkali metal secondary battery is a sodium ion secondary battery, the active material of the positive electrode is selected from NaMn (1-x-y) Ni y M x O2 (0 ≤ x, y ≤ 1, M is Cu, Fe, Co, sodium manganate, sodium vanadium phosphate, sodium fluorovanadium phosphate, sodium iron phosphate, sodium manganese phosphate, sodium iron sulfate, Na x MnFe(CN)6 (0 < x ≤ 2), and the active material of the negative electrode is selected from at least one of hard carbon, carbon black, amorphous carbon, graphite, SnS2, Na2Ti3O7, silicon-based materials, metal oxides, metal sulfides or metallic sodium.

Images