Cyclic ether-based alkali metal salt, electrolyte, and alkali metal-based battery thereof

Abstract

This invention relates to the field of alkali metal-based battery technology, and more particularly to a cyclic ether-based alkali metal salt, an electrolyte, and an alkali metal-based battery thereof. The cyclic ether-based alkali metal salt has the following general structural formula (I): Formula (I); wherein, A + For Li + Na + or K + Z1 and Z2 are independently sulfonyl groups or single bonds; at least one of R1 and R2 is selected from cyclic ether groups; the cyclic ether group is a cyclic ether group with 1-10 oxygen atoms. The cyclic ether alkali metal salt of the present invention utilizes the ring-opening polymerization ability of the cyclic ether group to provide catalytic sites for the transition metal at the positive electrode interface during the charging process of the alkali metal-based battery, forming a special anionic polymerization CEI interface. This interface can effectively passivate the positive electrode interface and improve the high-voltage resistance and cycle stability of the battery.

Description

Technical Field

[0001] This invention relates to the field of alkali metal-based battery technology, and in particular to a cyclic ether-based alkali metal salt, an electrolyte, and an alkali metal-based battery thereof. Background Technology

[0002] With the development of renewable energy systems, people have increasingly higher requirements for energy conversion and storage. Alkali metal-based battery systems, represented by lithium-ion batteries, have stood out among many battery systems due to their high energy density, long effective lifespan, and environmental friendliness, successfully occupying fields such as consumer electronics, new energy vehicles, and energy storage, becoming an indispensable component in people's lives and industrial production. As the application scope of lithium-ion batteries gradually expands, the required energy density and power density of batteries are becoming increasingly higher, especially placing high demands on the rapid cycling performance under fast charging and discharging conditions. The bottleneck of rapid cycling performance lies in the charge transfer kinetics at the electrode interface and the ionic conductivity of the electrolyte. Slow ion migration kinetics and significantly increased overpotential during cycling at high current densities severely limit the battery's rapid cycling capability and safety.

[0003] Currently, most publicly reported electrolyte research focuses on improving rapid cycling performance by optimizing electrolyte solvents or adding functional additives. Patent CN111193071A discloses an electrolyte formulation containing seven additives to improve the room-temperature fast-charging performance of batteries. However, this method uses a complex additive formulation, leading to complex electrolyte preparation processes and high costs. Furthermore, polystyrene (PS) in the additives is a carcinogen and its use has been restricted by countries such as the EU, seriously affecting the safe use of batteries. A related literature (Advanced Energy Materials, 2020, 10(22):2000368) proposes an electrolyte for high-rate cycling in LiNi... 0.8 Co 0.1 Mn 0.1 The O2 / Gr battery only released a specific capacity of 30 mAh / g under the 5C charging and 0.2C discharging test conditions.

[0004] This shows that current research on electrolytes for fast-cycling alkali metal-based batteries is far from meeting the demand. Summary of the Invention

[0005] This invention provides a cyclic ether-based alkali metal salt, an electrolyte, and an alkali metal-based battery thereof, to address the problem that the slow ion migration kinetics of existing electrolytes cannot meet the rapid cycling requirements of alkali metal-based batteries.

[0006] According to a first aspect of the present invention, the present invention provides a cyclic ether alkali metal salt having the following general structural formula (I): Formula (I); Among them, A + For Li + Na + or K + Z1 and Z2 are independently sulfonyl groups or single bonds; at least one of R1 and R2 is selected from cyclic ether groups; the cyclic ether group is a cyclic ether group with 1-10 oxygen atoms.

[0007] In the above-described scheme, the cyclic ether-based alkali metal salt of the present invention can be used as a main electrolyte salt or an additive in the electrolyte. This cyclic ether-based alkali metal salt contains cyclic ether groups. Utilizing the ring-opening polymerization ability of the cyclic ether groups, the transition metal at the positive electrode interface during the charging process of the alkali metal-based battery provides catalytic sites, initiating the ring-opening polymerization of the cyclic ether groups to form a special anionic polymerization CEI interface. This interface can effectively passivate the positive electrode interface, improving the battery's high-voltage resistance and cycle stability. More importantly, the CEI generated by anionic polymerization has a strong binding ability to alkali metal cations, which is beneficial to the cation interface desolvation kinetics, significantly reducing the charge transfer impedance under fast charging and discharging conditions, thereby significantly improving the capacity and cycle performance of the alkali metal-based battery under high-rate charge and discharge conditions. Furthermore, the sulfonyl group contained in the cyclic ether-based alkali metal salt of the present invention can significantly improve the battery interface stability by suppressing side reactions at the positive electrode-electrolyte interface and promoting uniform lithium deposition, thereby further improving the battery's cycle stability.

[0008] In order to better improve the rate performance and cycle stability of the battery, the cyclic ether group is further defined as a cyclic ether group with 1-10 oxygen atoms.

[0009] In some specific embodiments, the cyclic ether group is a cyclic ether group having 1-5 oxygen atoms. Preferably, the cyclic ether group is a cyclic ether group having 1-3 oxygen atoms.

[0010] Further, the cyclic ether group has 2-15 carbon atoms. In some specific embodiments, the cyclic ether group has 2-10 carbon atoms. Preferably, the cyclic ether group has 2-6 carbon atoms.

[0011] Further, the cyclic ether group is an alkyl-substituted or unsubstituted cyclic ether group with 1 to 10 carbon atoms. When the cyclic ether group is an alkyl-substituted cyclic ether group with 1 to 10 carbon atoms, there may be one or more alkyl substituents. In some specific embodiments, the cyclic ether group is an alkyl-substituted cyclic ether group with 1 to 3 carbon atoms, and the number of alkyl substituents is two.

[0012] Preferably, the cyclic ether group includes one or more of ethylene oxide, oxetyl, tetrahydrofuranyl, tetrahydropyranyl, dioxopentyl, 1,3-dioxanecycloyl, 1,4-dioxanecycloyl, and trioxanecyclohexyl.

[0013] In this invention, R1 and R2 in a cyclic ether alkali metal salt can both be selected from cyclic ether groups. When R1 and R2 are both selected from cyclic ether groups, the groups can be the same or different.

[0014] In this invention, only one of R1 and R2 in a cyclic ether alkali metal salt can be selected from a cyclic ether group. In some specific embodiments, R1 is selected from a cyclic ether group; R2 is selected from one or more of the following: halogen (fluorine, chlorine, bromine, iodine), halogen-substituted or unsubstituted alkyl groups with 1 to 10 carbon atoms, alkoxy groups, alkenoxy groups, cyano groups, phenyl groups, fluorophenyl groups, trimethylsilyl groups, trifluoromethylsilyl groups, cyclotriphosphazene groups, fluorocyclotriphosphazene groups, isocyanate groups, and lithium atoms. In this cyclic ether alkali metal salt with such a structure, the cyclic ether group can better exert synergistic effects with other groups, thereby better improving the rate performance and cycle stability of the battery.

[0015] Furthermore, the compound represented by the general formula (I) is selected from one or more of formulas I-1 to I-12:

[0016] Preferably, the compound represented by the general formula (I) is selected from one or both of formula I-1 or formula I-2.

[0017] The cyclic ether alkali metal salts of the present invention can be prepared by synthetic methods known in the art. For example, when the cyclic ether alkali metal salt is a compound of formula I-2, its preparation method includes the following steps: The first step involves dissolving oxetane-3-amine, potassium carbonate, and trifluoromethanesulfonyl chloride in a solvent (e.g., acetonitrile). After the reaction, the resulting mixture is filtered, and the filtrate is rotary evaporated to obtain the potassium salt product. The preparation of the corresponding lithium or sodium salt requires a second step: dissolving the potassium salt product in a solvent, followed by adding lithium tetrafluoroborate or sodium tetrafluoroborate to perform a substitution reaction to obtain the target lithium or sodium salt product. The synthetic route is shown below: .

[0018] For example, when the cyclic ether alkali metal salt is a compound of formula I-3, its preparation method includes the following steps: The first step involves dissolving tetrahydrofuran-3-amine, potassium carbonate, and trifluoromethanesulfonyl chloride in a solvent (e.g., acetonitrile). After the reaction, the resulting mixture is filtered, and the filtrate is rotary evaporated to obtain the potassium salt product. The preparation of the corresponding lithium or sodium salt requires a second step: dissolving the potassium salt product in a solvent, and then adding lithium tetrafluoroborate or sodium tetrafluoroborate to perform a substitution reaction to obtain the target lithium or sodium salt product. The synthetic route is shown below: .

[0019] According to a second aspect of the present invention, an electrolyte is also provided, comprising a matrix and the aforementioned cyclic ether alkali metal salt; the matrix is ​​an organic solvent or a solid polymer; the cyclic ether alkali metal salt serves as a main electrolyte salt and / or an additive. Specifically, the cyclic ether alkali metal salt can serve as the main electrolyte salt, or as an additive to the electrolyte, or simultaneously as both the main electrolyte salt and an additive. It should be noted that the use of the cyclic ether alkali metal salt as the main electrolyte salt and / or additive does not preclude the inclusion of other components that can serve as electrolyte salts and / or additives in the electrolyte.

[0020] Preferably, the organic solvent is at least one selected from the following organic solvents: ethylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, propylene carbonate, vinylene carbonate, fluoroethylene carbonate, diethyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyltetrahydrofuran, tetrahydropyran, 1,4-dioxane, and 1,3-dioxane. In some specific embodiments, the organic solvent is ethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, tetrahydrofuran, or methyltetrahydrofuran.

[0021] Preferably, the solid polymer is at least one of the following solid polymers: polyethylene glycol, polyvinylidene fluoride, polyethylene, polypropylene, polytetrafluoroethylene, polyacrylonitrile, and polyphosphazene.

[0022] Furthermore, the amount of the cyclic ether alkali metal salt used is 0.01-80%, and the amount used is based on the mass of the electrolyte.

[0023] When the cyclic ether alkali metal salt is used as the main electrolyte salt, its dosage is 20% to 80%. In some specific embodiments, the dosage of the cyclic ether alkali metal salt as the main electrolyte salt is 25% to 50%.

[0024] When the cyclic ether alkali metal salt is used as an additive, its dosage is 0.01% to 20%. In some specific embodiments, the cyclic ether alkali metal salt is used as an additive, its dosage is 0.1% to 10%. In some specific embodiments, the cyclic ether alkali metal salt is used as an additive, its dosage is 0.15% to 5%. In some specific embodiments, the cyclic ether alkali metal salt is used as an additive, its dosage is 1% to 3%.

[0025] Furthermore, when the cyclic ether alkali metal salt is used as the primary electrolyte salt, the electrolyte also includes other auxiliary electrolyte salts besides the cyclic ether alkali metal salt. These other auxiliary electrolyte salts include one or more of the following: bis(fluorosulfonyl)imide salt, bis(trifluoromethanesulfonyl)imide salt, hexafluorophosphate, difluorophosphate, trifluoromethanesulfonate, difluorooxalate borate, tetrafluoroborate, and bis(oxalate borate). In some specific embodiments, the other auxiliary electrolyte salt besides the cyclic ether alkali metal salt is lithium difluorooxalate borate.

[0026] Furthermore, when the cyclic ether alkali metal salt is used as an additive, the additive also includes other additives besides the cyclic ether alkali metal salt. These other additives include one or more of the following: alkali metal nitrates, alkali metal perchlorates, alkali metal sulfates, alkali metal carbonates, alkali metal bis(fluorosulfonyl)imide salts, alkali metal bis(trifluoromethanesulfonyl)imide salts, alkali metal hexafluorophosphates, alkali metal difluorophosphates, alkali metal trifluoromethanesulfonates, alkali metal difluorooxalate borate, alkali metal tetrafluoroborate, and alkali metal bis(oxalate borate). The alkali metal is Li, Na, or K. In some specific embodiments, the other additives besides the cyclic ether alkali metal salt account for 0.01% to 20% of the total electrolyte mass.

[0027] In some specific embodiments, the additives other than the cyclic ether alkali metal salt are one or more of lithium difluorooxalate borate, lithium nitrate, and lithium perchlorate. In some specific embodiments, the ratio of the cyclic ether alkali metal salt to the other additives is (4-50):(10-25).

[0028] In some specific embodiments of the present invention, the lithium salt compound of the cyclic ether alkali metal salt is used as an additive, the electrolyte salt is lithium bis(fluorosulfonyl)imide or lithium bis(trifluoromethanesulfonyl)imide, the mass content of which in the electrolyte is 15-35%, the organic solvent is one or more of ethylene glycol dimethyl ether, tetrahydrofuran or methyltetrahydrofuran, and the mass content of the cyclic ether alkali metal salt in the electrolyte is 0.4-4%.

[0029] In some specific embodiments of the present invention, the lithium salt compound of the cyclic ether alkali metal salt is used as an additive, without the presence of other additives, the electrolyte salt is lithium bis(fluorosulfonyl)imide or lithium bis(trifluoromethanesulfonyl)imide, the mass content of which in the electrolyte is 20-35%, the organic solvent is ethylene glycol dimethyl ether, and the mass content of the cyclic ether alkali metal salt in the electrolyte is 1-3%.

[0030] In some specific embodiments of the present invention, the lithium salt compound of the cyclic ether alkali metal salt is used as the main electrolyte salt, and its mass percentage in the electrolyte is 25-50%; the organic solvent is tetraethylene glycol dimethyl ether or tetrahydrofuran, and the additive is lithium nitrate and / or lithium difluorooxalate borate, and the additive's mass percentage in the electrolyte is 0.5-6%.

[0031] In some specific embodiments of the present invention, the lithium salt compound of the cyclic ether alkali metal salt is used as the main electrolyte salt, the organic solvent is tetraethylene glycol dimethyl ether, the additives are lithium nitrate and lithium difluorooxalate borate, the total mass of lithium nitrate and lithium difluorooxalate borate in the electrolyte accounts for 2-6% of the total mass, preferably 3-5%, and the mass ratio of lithium nitrate to lithium difluorooxalate borate is 1:(2-4).

[0032] According to a third aspect of the present invention, the present invention also provides an alkali metal-based battery comprising the electrolyte described above.

[0033] The alkali metal-based battery described in this invention can be an alkali metal battery or an alkali metal ion battery.

[0034] The alkali metal-based battery described in this invention can be a liquid alkali metal-based battery or a solid alkali metal-based battery. Correspondingly, the electrolyte is a non-aqueous liquid electrolyte or a polymer solid electrolyte.

[0035] The alkali metal-based battery of the present invention is not limited in shape and can be cylindrical, aluminum-cased, plastic-cased, or pouch-cased.

[0036] Furthermore, when the alkali metal-based battery of the present invention is a liquid alkali metal-based battery, the alkali metal-based battery further includes a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode. The positive electrode may be selected from one or more of the following: sulfur-containing positive electrode materials, selenium-containing positive electrode materials, alkali metal cobaltates, alkali metal iron phosphates, alkali metal manganese iron phosphates, alkali metal manganates, alkali metal nickel iron manganates, Prussian blue, alkali metal nickel manganates, alkali metal nickel cobalt manganates, alkali metal nickel cobalt aluminum phosphates, alkali metal vanadium phosphates, and alkali metal fluorovanadium phosphates.

[0037] Furthermore, the negative electrode is selected from lithium metal, lithium alloy, sodium metal, sodium alloy, potassium metal, potassium alloy, silicon, graphite, hard carbon, and soft carbon, etc.

[0038] Furthermore, the diaphragm is a polypropylene, polyethylene film, or a glass fiber diaphragm.

[0039] Furthermore, when the alkali metal-based battery described in this invention is a solid-state alkali metal-based battery, no separator assembly is required when assembling the solid-state battery using a solid electrolyte.

[0040] This invention provides a cyclic ether-based alkali metal salt that can be used as an electrolyte. Utilizing the ring-opening polymerization capability of the cyclic ether groups in the cyclic ether-based alkali metal salt, a transition metal at the positive electrode interface during the charging process of an alkali metal-based battery provides catalytic sites, initiating the ring-opening polymerization of the cyclic ether groups to form a special anionic polymerization CEI interface. This interface effectively passivates the positive electrode interface, improving the battery's high-voltage withstand performance and cycle stability. Furthermore, the CEI generated by anionic polymerization has a strong binding ability to alkali metal cations, which is beneficial to the cation interface desolvation kinetics, significantly reducing charge transfer impedance under fast charge and discharge conditions, thereby significantly improving the capacity and cycle performance of alkali metal-based batteries under high-rate charge and discharge conditions. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0042] Figure 1 Performance graphs of NCM811 / Li batteries prepared using the electrolytes of Example 1 and Comparative Example 1 of this invention at different charge and discharge rates.

[0043] Figure 2 The 5C fast cycling stability graphs of NCM811 / Li batteries prepared using the electrolytes of Example 1 and Comparative Example 1 of this invention. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0045] Unless otherwise specified, the technical means used in the embodiments of the present invention are all conventional means well known to those skilled in the art.

[0046] The organic solvents, alkali metal salt electrolytes and additives used in the embodiments and comparative examples of this invention are all battery grade. In the compound represented by formula (I), A is Li. The cyclic ether alkali metal salts prepared in this invention have all undergone multiple purification steps and strict drying.

[0047] In the following examples, the preparation of the electrolyte and the battery assembly process were carried out in a glove box filled with argon gas of 99.999% purity, with a moisture content of less than 0.1 ppm and a temperature of room temperature.

[0048] The compounds of formulas I-1 to I-12 used in the following examples and comparative examples were synthesized using the following methods: The preparation method of the compound of formula I-1 may include the following steps: In the first step, 59 g of ethylene oxide-2-amine and 168.5 g of trifluoromethanesulfonyl chloride were dissolved in 1500 ml of acetonitrile. After the sample was completely mixed, 420 g of potassium carbonate was added, and the mixture was then sealed and stirred at room temperature for 30 h. After the reaction was complete, the resulting mixture was filtered, and the solvent was removed from the filtrate under vacuum to obtain the potassium salt product. The preparation of the corresponding lithium or sodium salt requires a second step: after dissolving the potassium salt product in a solvent, an equimolar amount of lithium tetrafluoroborate or sodium tetrafluoroborate was added to perform a cation exchange reaction to obtain the target lithium or sodium salt product. MS: [M] - m / z = 189.98.

[0049] The preparation method of compound I-2 may include the following steps: similar to the preparation method of compound I-1, except that ethylene oxide-2-amine is replaced with an equimolar amount of oxetane-3-amine. MS: [M] - m / z = 203.99.

[0050] The preparation method of compound I-3 may include the following steps: similar to the preparation method of compound I-1, except that ethylene oxide-2-amine is replaced with an equimolar amount of tetrahydrofuran-3-amine. MS: [M] - m / z = 218.01.

[0051] The preparation method of compound I-4 may include the following steps: similar to the preparation method of compound I-1, except that ethylene oxide-2-amine is replaced with an equimolar amount of tetrahydropyran-4-amine. MS: [M] - m / z = 232.03.

[0052] The preparation method of compounds of formula I-5 may include the following steps: similar to the preparation method of compound I-1, except that ethylene oxide-2-amine is replaced with an equimolar amount of 1,3-dioxolane-2-amine. MS: [M] - m / z = 219.99.

[0053] The preparation method of compounds of formula I-6 may include the following steps: similar to the preparation method of compound I-1, except that ethylene oxide-2-amine is replaced with an equimolar amount of 1,3-dioxane-5-amine. MS: [M] - m / z = 234.01.

[0054] The preparation method of compounds of formula I-7 may include the following steps: similar to the preparation method of compound I-1, except that ethylene oxide-2-amine is replaced with an equimolar amount of 1,3,5-trioxane-2-amine. MS: [M] - m / z = 235.98.

[0055] The preparation method of compounds of formula I-8 may include the following steps: similar to the preparation method of compound I-1, except that ethylene oxide-2-amine is replaced with an equimolar amount of tetrahydrofuran-3-sulfonamide. MS: [M] - m / z = 281.97.

[0056] The preparation method of compounds of formula I-9 may include the following steps: similar to the preparation method of compound I-1, except that ethylene oxide-2-amine is replaced with an equimolar amount of 2,5-dimethyltetrahydrofuran-3-amine. MS: [M] - m / z = 246.04.

[0057] The preparation method of compounds of formula I-10 may include the following steps: similar to the preparation method of compounds I-8, except that trifluoromethanesulfonyl chloride is replaced with an equimolar amount of fluorosulfonyl chloride. MS: [M] - m / z = 231.98.

[0058] The preparation method of compound I-11 may include the following steps: similar to the preparation method of compound I-2, except that trifluoromethanesulfonyl chloride is replaced with an equimolar amount of tetrahydrofuran-3-sulfonyl chloride. MS: [M] - m / z = 206.05.

[0059] The preparation method of compound I-12 may include the following steps: similar to the preparation method of compound I-11, except that the oxetane-3-amine is replaced with an equimolar amount of tetrahydropyran-4-sulfonamide. MS: [M] - m / z = 298.04.

[0060] Example 1 This embodiment provides an electrolyte, using a cyclic ether alkali metal salt of Formula I-1 as an additive, comprising 1000 mL of the organic solvent ethylene glycol dimethyl ether, 374 g of the electrolyte salt lithium difluorosulfonylimide, and 19.7 g of additive.

[0061] The preparation method is as follows: In a glove box filled with argon, take 374g of lithium difluorosulfonylimide, 19.7g of the cyclic ether alkali metal salt of the above formula I-1, and 1000mL of ethylene glycol dimethyl ether, and stir until a homogeneous, clear and transparent solution is obtained.

[0062] Example 2 This embodiment provides an electrolyte, using the cyclic ether alkali metal salt of Formula I-2 as an additive, comprising 1000 mL of the organic solvent ethylene glycol dimethyl ether, 287 g of the electrolyte salt lithium bis(trifluoromethanesulfonyl)imide, and 21.1 g of additive.

[0063] The preparation method is as follows: In a glove box filled with argon, take 287g of lithium bis(trifluoromethanesulfonyl)imide, 21.1g of the cyclic ether alkali metal salt of the above formula I-2, and 1000mL of ethylene glycol dimethyl ether, and stir until a homogeneous, clear and transparent solution is obtained.

[0064] Example 3 This embodiment provides an electrolyte, which uses the cyclic ether alkali metal salt of Formula I-2 as the main electrolyte salt, including 1000 mL of organic solvent tetraethylene glycol dimethyl ether, 422 g of the cyclic ether alkali metal salt of electrolyte Formula I-2, 43 g of lithium difluorooxalate borate and 14 g of additive lithium nitrate.

[0065] The preparation method is as follows: In a glove box filled with argon, take 422g of the cyclic ether alkali metal salt of the above formula I-2, 14g of lithium nitrate, 43g of lithium difluorooxalate borate, and 1000mL of tetraethylene glycol dimethyl ether, and stir until a homogeneous, clear and transparent solution is obtained.

[0066] Example 4 This embodiment provides an electrolyte, using the cyclic ether alkali metal salt of Formula I-3 as an additive, comprising 1000 mL of the organic solvent tetrahydrofuran, 187 g of the electrolyte lithium difluorosulfonylimide, 45 g of the cyclic ether alkali metal salt of Formula I-3, and 21 g of the additive lithium perchlorate.

[0067] The preparation method is as follows: In a glove box filled with argon, take 187g of lithium difluorosulfonylimide, 21g of lithium perchlorate, 45g of the cyclic ether alkali metal salt of the above formula I-3, and 1000mL of tetrahydrofuran, and stir until a homogeneous, clear and transparent solution is obtained.

[0068] Example 5 This embodiment provides an electrolyte, using the cyclic ether alkali metal salt of Formula I-5 as an additive, comprising 1000 mL of organic solvent methyltetrahydrofuran, 187 g of electrolyte lithium difluorosulfonylimide, 4.5 g of the cyclic ether alkali metal salt of Formula I-5, and 14 g of additive lithium nitrate.

[0069] The preparation method is as follows: In a glove box filled with argon, take 187g of lithium difluorosulfonylimide, 14g of lithium nitrate, 4.5g of the cyclic ether alkali metal salt of formula I-5 above, and 1000mL of methyltetrahydrofuran, and stir until a homogeneous, clear and transparent solution is obtained.

[0070] Example 6 This embodiment provides an electrolyte, which uses the cyclic ether alkali metal salt of Formula I-8 as the main electrolyte salt, including 1000 mL of the organic solvent tetrahydrofuran, 750 g of the cyclic ether alkali metal salt of electrolyte Formula I-8, and 14 g of the additive lithium nitrate.

[0071] The preparation method is as follows: In a glove box filled with argon, take 750g of cyclic ether alkali metal salt of formula I-8, 14g of lithium nitrate, and 1000mL of tetrahydrofuran, and stir until a homogeneous, clear, and transparent solution is obtained.

[0072] Example 7 This embodiment provides an electrolyte, using the cyclic ether alkali metal salt of Formula I-10 as an additive, comprising 1000 mL of organic solvent ethylene glycol dimethyl ether, 374 g of electrolyte lithium difluorosulfonylimide, and 23.9 g of additive.

[0073] The preparation method is as follows: In a glove box filled with argon, take 374g of lithium difluorosulfonylimide, 23.9g of the cyclic ether alkali metal salt of formula I-10 above, and 1000mL of ethylene glycol dimethyl ether, and stir until a homogeneous, clear and transparent solution is obtained.

[0074] Example 8 This embodiment provides an electrolyte, using a cyclic ether alkali metal salt of formula I-12 as an additive, comprising 1000 mL of organic solvent ethylene glycol dimethyl ether, 374 g of electrolyte lithium difluorosulfonylimide, and 30.5 g of additive.

[0075] The preparation method is as follows: In a glove box filled with argon, take 374g of lithium difluorosulfonylimide, 30.5g of the cyclic ether alkali metal salt of the above formula I-12, and 1000mL of ethylene glycol dimethyl ether, and stir until a homogeneous, clear and transparent solution is obtained.

[0076] Example 9 This embodiment provides an electrolyte that differs from Embodiment 1 only in that an equimolar amount of the cyclic ether alkali metal salt of Formula I-2 is used instead of the cyclic ether alkali metal salt of Formula I-1.

[0077] Example 10 This embodiment provides an electrolyte that differs from Embodiment 1 only in that an equimolar amount of the cyclic ether alkali metal salt of Formula I-3 is used instead of the cyclic ether alkali metal salt of Formula I-1.

[0078] Example 11 This embodiment provides an electrolyte that differs from Embodiment 1 only in that an equimolar amount of the cyclic ether alkali metal salt of Formula I-4 is used instead of the cyclic ether alkali metal salt of Formula I-1.

[0079] Comparative Example 1 This comparative example provides a lithium battery electrolyte comprising 374g of lithium bis(fluorosulfonyl)imide and 1000mL of ethylene glycol dimethyl ether.

[0080] The preparation method is as follows: In an argon-filled glove box, take 374g of lithium difluorosulfonyl imide and 1000mL of ethylene glycol dimethyl ether, and stir until a homogeneous, clear, and transparent solution is obtained.

[0081] Comparative Example 2 This comparative example provides a lithium battery electrolyte comprising 187g lithium difluorosulfonylimide, 14g lithium nitrate, 43g lithium difluorooxalate borate, and 1000mL tetraethylene glycol dimethyl ether.

[0082] The preparation method is as follows: In an argon-filled glove box, take 187g of lithium difluorosulfonylimide, 14g of lithium nitrate, 43g of lithium difluorooxalate borate, and 1000mL of tetraethylene glycol dimethyl ether, and stir until a homogeneous, clear, and transparent solution is obtained.

[0083] Comparative Example 3 This comparative example provides a lithium battery electrolyte comprising 187g of lithium bis(fluorosulfonyl)imide, 21g of lithium perchlorate, and 1000mL of tetrahydrofuran.

[0084] The preparation method is as follows: In an argon-filled glove box, take 187g of lithium difluorosulfonylimide, 21g of lithium perchlorate, and 1000mL of tetrahydrofuran, and stir until a homogeneous, clear, and transparent solution is obtained.

[0085] Comparative Example 4 This comparative example provides a lithium battery electrolyte, which differs from Example 1 in that it uses an equimolar amount of lithium bis(trifluoromethanesulfonyl)imide to replace the cyclic ether alkali metal salt of Formula I-1.

[0086] Performance testing The electrolytes prepared in the above embodiments and comparative examples were assembled into batteries and then subjected to cycle performance testing, as follows: This performance test uses lithium-ion batteries to represent alkali metal-based batteries, with LiNi as an example. 0.8 Co 0.1 Mn 0.1O2 (NCM811) was used as the positive electrode, lithium metal as the negative electrode, and aluminum foil as the positive electrode current collector. A Celgard 2325 separator was used. Button half-cells were assembled in a glove box and tested after 24 hours of rest. The battery was activated by three charge-discharge cycles at 1 / 5C rate between 3.0V and 4.3V at a constant temperature of 25°C. Subsequent charge-discharge cycles at different rates of 1C, 2C, 5C, and 10C were performed. Rapid cycle stability tests were conducted at constant rates of 2C and 5C. Long-term charge-discharge cycles at 2C and 5C rates at room temperature were performed; the results are shown in Table 1. High-voltage cycle stability tests were conducted at 25°C at a constant temperature, with long-term charge-discharge cycles at 1 / 2C rate between 3.0V and 4.5V or 4.6V; the results are shown in Table 2.

[0087] Table 1. Cycling results of the NCM811 / Li half-cells assembled in the examples and comparative examples at 2C and 5C.

[0088] Figure 1 The graph shows the performance of NCM811 / Li batteries prepared using the electrolytes of Example 1 and Comparative Example 1 at different charge and discharge rates. Figure 2 The graph shows the 5C fast cycling stability of NCM811 / Li batteries prepared using the electrolytes of Example 1 and Comparative Example 1.

[0089] Table 2 shows the high-voltage cycling results at 4.5V and 4.6V for the NCM811 / Li half-cells assembled in the examples and comparative examples.

[0090] From Tables 1-2 and Figures 1-2 As can be seen, the electrolyte with a cyclic ether alkali metal salt added in this invention can simultaneously and significantly improve the cycle stability of NCM811 / Li half-cells under fast charging and high voltage, with performance far exceeding that of comparative examples without this additive or using other additives. Data shows that this invention effectively suppresses capacity decay of the battery under harsh conditions such as 5C high-rate fast charging and 4.6V extreme high voltage by forming a stable protective interface on the positive electrode surface. Among these, Examples 1, 2, 4, and 9 all exhibit superior overall performance compared to other examples. Example 1 stands out, achieving a capacity retention rate of 98% and 97% after 200 cycles of 2C and 5C fast charging, respectively, while maintaining top-level performance of 92% and 89% under 4.5V and 4.6V high-voltage cycling, demonstrating the best overall performance among all test groups.

[0091] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A cyclic ether-based alkali metal salt, characterized in that, It has the following general structural formula (I): Equation (I); Among them, A + For Li + Na + or K + Z1 and Z2 are independently sulfonyl groups or single bonds; at least one of R1 and R2 is selected from cyclic ether groups; the cyclic ether group is a cyclic ether group with 1-10 oxygen atoms.

2. The cyclic ether alkali metal salt according to claim 1, characterized in that, The cyclic ether group has 2-15 carbon atoms.

3. The cyclic ether alkali metal salt according to claim 1 or 2, characterized in that, The cyclic ether group is a substituted or unsubstituted cyclic ether group. When substituted, the substituent is an alkyl group with 1 to 10 carbon atoms.

4. The cyclic ether alkali metal salt according to any one of claims 1-3, characterized in that, The cyclic ether group includes one or more of the following: ethylene oxide, oxetyl, tetrahydrofuranyl, tetrahydropyranyl, dioxopentyl, 1,3-dioxane, 1,4-dioxane, and trioxanehexyl.

5. The cyclic ether alkali metal salt according to claim 1, characterized in that, R1 is selected from cyclic ether groups; R2 is selected from one or more of the following groups: halogen, halogen-substituted or unsubstituted alkyl, alkoxy, alkenoxy, alkynoxy, cyano, phenyl, fluorophenyl, trimethylsilyl, trifluoromethylsilyl, cyclotriphosphazene, fluorocyclotriphosphazene, isocyanate group, and lithium atom, having 1 to 10 carbon atoms.

6. The cyclic ether alkali metal salt according to any one of claims 1-5, characterized in that, The compound represented by the general formula (I) is selected from one or more of formulas I-1 to I-12:

7. An electrolyte, characterized in that, Includes a matrix and the cyclic ether alkali metal salt according to any one of claims 1-6; the matrix is ​​an organic solvent or a solid polymer; Preferably, the amount of the cyclic ether alkali metal salt is 0.01 to 80% based on the mass of the electrolyte.

8. The electrolyte according to claim 7, characterized in that, It also includes one or more of the following: difluorosulfonylimide salt, ditrifluoromethylsulfonylimide salt, hexafluorophosphate, difluorophosphate, trifluoromethylsulfonate, difluorooxalate borate, tetrafluoroborate, and dioxalate borate.

9. The electrolyte according to claim 7 or 8, characterized in that, It also includes one or more of the following: alkali metal nitrates, alkali metal perchlorates, alkali metal sulfates, alkali metal carbonates, alkali metal bis(fluorosulfonyl)imide salts, alkali metal bis(trifluoromethanesulfonyl)imide salts, alkali metal hexafluorophosphates, alkali metal difluorophosphates, alkali metal trifluoromethanesulfonates, alkali metal difluorooxalate borates, alkali metal tetrafluoroborates, and alkali metal bis(oxalate borates).

10. An alkali metal-based battery, characterized in that, Includes the electrolyte as described in any one of claims 7-9.

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