Electrolyte additive combinations, electrolytes for electrochemical energy storage units and their applications

Abstract

This invention provides an electrolyte additive combination, an electrolyte for electrochemical energy storage units, and their applications. The electrolyte additive combination includes a monocyano compound and a tricyano compound. The monocyano compound is selected from additive A and / or additive B. Both the cyano group and the phosphate ester group in additive A or additive B form a complex with the positive electrode metal ions, effectively protecting the positive electrode and forming a phosphorus-based compound protective film at the negative electrode. The cyano group in the tricyano compound also forms a complex with the positive electrode metal ions, effectively protecting the positive electrode. The combination of the monocyano compound and the tricyano compound has a synergistic effect, effectively improving the battery's high-temperature storage performance and high-temperature cycle performance.

Description

Technical Field

[0001] This invention belongs to the field of electrolyte materials technology, and relates to an electrolyte additive combination, an electrolyte for electrochemical energy storage units, and their applications. Background Technology

[0002] Lithium-ion batteries are widely used in consumer electronics, power, and energy storage. To meet the demand for high capacity, developing high-voltage lithium batteries has become an effective means of improving energy density. The accompanying high-voltage electrolyte uses a large number of positive electrode protection additives, among which nitrile additives are indispensable. Specifically, the combination of dinitrile-based and trinitrile-based compounds can achieve better overall battery performance. However, at voltages of 4.53V and higher, the combination of dinitrile-based and trinitrile-based compounds is insufficient in terms of high-temperature storage and high-temperature cycling performance of lithium batteries, making it difficult to meet application requirements.

[0003] Therefore, there is an urgent need to develop an electrolyte system to solve the above problems. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide an electrolyte additive combination, an electrolyte for electrochemical energy storage units, and their applications. When this electrolyte additive combination is added to the electrolyte, it can effectively improve the high-temperature storage performance and high-temperature cycling performance of the electrochemical energy storage unit.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides an electrolyte additive combination comprising a monocyano compound and a tricyano compound, wherein the monocyano compound is selected from additive A and / or additive B, wherein the structure of additive A is shown in Formula I, and the structure of additive B is shown in Formula II.

[0007]

[0008] In Formula I, R1 and R2 are each independently selected from alkyl groups having 1-6 carbon atoms, fluoroalkyl groups having 1-6 carbon atoms, or cycloalkyl groups having 3-6 carbon atoms;

[0009] In Formula II, R3 and R4 are each independently selected from alkyl groups having 1-6 carbon atoms, fluoroalkyl groups having 1-6 carbon atoms, or cycloalkyl groups having 3-6 carbon atoms.

[0010] This invention modifies the composition of an electrolyte additive combination, which includes a monocyano compound and a tricyano compound. The monocyano compound is selected from additive A and / or additive B. Both the cyano group and the phosphate ester group in additive A or additive B form a complex with the positive electrode metal ions, effectively protecting the positive electrode and forming a phosphorus-based compound protective film at the negative electrode. The cyano group in the tricyano compound also forms a complex with the positive electrode metal ions, effectively protecting the positive electrode. Experiments have shown that the combined use of the monocyano compound and the tricyano compound, when applied to an electrochemical energy storage unit, can exert a synergistic effect, effectively improving the battery's high-temperature storage performance and high-temperature cycle performance.

[0011] In this invention, the carbon atom number range defined by R1, R2, R3, and R4 refers to any integer within the defined range. The carbon atom number can be 1-6, and can be 1, 2, 3, 4, 5, or 6. The carbon atom number can be 3-6, and can be 3, 4, 5, or 6. R1, R2, R3, and R4 can be the same or different. The alkyl group can be a straight-chain or branched alkyl group.

[0012] As an optional embodiment of the present invention, R1, R2, R3 and R4 are each independently selected from alkyl groups having 1-4 carbon atoms, fluoroalkyl groups having 1-4 carbon atoms, or cycloalkyl groups having 3-6 carbon atoms.

[0013] As an optional embodiment of the present invention, R1 is selected from alkyl groups having 1-4 carbon atoms or fluoroalkyl groups having 1-4 carbon atoms.

[0014] As an optional embodiment of the present invention, R2 is selected from alkyl groups having 1-4 carbon atoms, fluoroalkyl groups having 1-4 carbon atoms, or cycloalkyl groups having 3-6 carbon atoms.

[0015] As an optional embodiment of the present invention, R3 is selected from alkyl groups having 1-4 carbon atoms, fluoroalkyl groups having 1-4 carbon atoms, or cycloalkyl groups having 3-6 carbon atoms.

[0016] As an optional embodiment of the present invention, R4 is selected from alkyl groups having 1-4 carbon atoms or fluoroalkyl groups having 1-4 carbon atoms.

[0017] As an optional embodiment of the present invention, the alkyl group having 1-6 carbon atoms is selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, tert-pentyl or n-hexyl.

[0018] As an optional embodiment of the present invention, the fluoroalkyl group having 1-6 carbon atoms is selected from 2-fluoroethyl, 2,2-difluoroethyl, 1,2-difluoroethyl, 2,2,2-trifluoroethyl, 1-fluoropropyl, 2-fluoropropyl, 2,2-difluoropropyl, 1,3-difluoropropyl, 3,3,3-trifluoropropyl, 2,2,3,3-tetrafluoropropyl, 2,2,3,3,3-pentafluoropropyl, 4-fluorobutyl, 4,4,4-trifluorobutyl, 3,3,4,4,4-pentafluorobutyl or 2,2,3,3,tetrafluorobutyl.

[0019] As an optional embodiment of the present invention, the cycloalkyl group having 3-6 carbon atoms is selected from cyclopropyl, cyclobutyl, cyclopentyl or cyclohexyl.

[0020] As an optional embodiment of the present invention, R1, R2, R3 and R4 are each independently selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, tert-pentyl, n-hexyl, 2-fluoroethyl, 2,2-difluoroethyl, 1,2-difluoroethyl, 2,2,2-trifluoroethyl, 1-fluoropropyl, 2-fluoropropyl, 2,2-difluoropropyl, 1,3-difluoropropyl, 3,3,3-trifluoropropyl, 2,2,3,3-tetrafluoropropyl, 2,2,3,3,3-pentafluoropropyl, 4-fluorobutyl, 4,4,4-trifluorobutyl, 3,3,4,4,4-pentafluorobutyl or 2,2,3,3,tetrafluorobutyl.

[0021] As an optional embodiment of the present invention, R1, R2, R3 and R4 are each independently selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, tert-pentyl or n-hexyl.

[0022] As an optional embodiment of the present invention, R1, R2, R3 and R4 are each independently selected from 2-fluoroethyl, 2,2-difluoroethyl, 1,2-difluoroethyl, 2,2,2-trifluoroethyl, 1-fluoropropyl, 2-fluoropropyl, 2,2-difluoropropyl, 1,3-difluoropropyl, 3,3,3-trifluoropropyl, 2,2,3,3-tetrafluoropropyl, 2,2,3,3,3-pentafluoropropyl, 4-fluorobutyl, 4,4,4-trifluorobutyl, 3,3,4,4,4-pentafluorobutyl or 2,2,3,3,tetrafluorobutyl.

[0023] As an optional embodiment of the present invention, R1 is selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, n-pentyl, isopentyl, tert-pentyl, n-hexyl or 2-fluoropropyl.

[0024] As an optional embodiment of the present invention, R2 is selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, n-pentyl, isopentyl, tert-pentyl, n-hexyl, cyclobutyl, cyclopentyl, cyclohexyl or 2,2,2-trifluoroethyl.

[0025] As an optional embodiment of the present invention, R3 is selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, n-pentyl, cyclohexyl, 2-fluoroethyl, 2-fluoropropyl or 2,2-difluoropropyl.

[0026] As an optional embodiment of the present invention, R4 is selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, n-pentyl, isopentyl, tert-pentyl, n-hexyl or 2-fluoropropyl.

[0027] In one optional embodiment of the present invention, the mass ratio of the monocyano compound to the tricyano compound is (0.2-3):(0.2-4). Typical but non-limiting mass ratios of the monocyano compound to the tricyano compound are 0.2:0.2, 0.2:0.5, 0.2:1, 0.2:1.5, 0.2:2, 0.2:2.5, 0.2:3, 0.2:3.5, 0.2:4, 0.5:0.2, 0.5:0.5, 0.5:1, 0.5:1.5, 0.5:2, 0.5:2.5, 0.5:3, 0.5:3.5, 0.5:4, 1:0.2, 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1.5:0.2, 1.5 The ratios are: 0.5, 1.5:1, 1.5:1.5, 1.5:2, 1.5:2.5, 1.5:3, 1.5:3.5, 1.5:4, 2:0.2, 2:0.5, 2:1, 2:1.5, 2:2, 2:2.5, 2:3, 2:3.5, 2:4, 2.5:0.2, 2.5:0.5, 2.5:1, 2.5:1.5, 2.5:2, 2.5:2.5, 2.5:3, 2.5:3.5, 2.5:4, 3:0.2, 3:0.5, 3:1, 3:1.5, 3:2, 3:2.5, 3:3, 3:3.5, or 3:4, etc. Further limiting the mass ratio of monocyano compounds to tricyano compounds helps to enhance the synergistic effect between them.

[0028] As an optional embodiment of the present invention, the additive A comprises at least one of the compounds having the following structures:

[0029]

[0030]

[0031]

[0032] As an optional embodiment of the present invention, additive A has the structure shown in Formula I. Its preparation method is as follows:

[0033] Phosphorus oxychloride, NC-R1-OH, and R2-OH were esterified to obtain an intermediate. After fluorination, the product is purified to obtain additive A. R1 and R2 are each independently selected from alkyl groups with 1-6 carbon atoms, fluoroalkyl groups with 1-6 carbon atoms, or cycloalkyl groups with 3-6 carbon atoms.

[0034] As an optional embodiment of the present invention, additive A-1 The preparation method is as follows:

[0035] (1) Esterification reaction

[0036] 76.7 g (0.5 mol) of phosphorus oxychloride and 153.4 g of 1,2-dichloroethane solvent were added to a 500 mL three-necked flask. The mixture was stirred and cooled to 15 °C. 23.0 g (0.5 mol) of ethanol was added dropwise over 30 min. Then, 35.5 g (0.5 mol) of 3-hydroxypropionitrile was added dropwise. After the addition of the starting materials was complete, the temperature was raised to 25 °C, and the reaction was continued for 90 min to obtain a reaction solution containing a chlorinated intermediate. The reaction solution was transferred to a 500 mL single-necked flask and concentrated under reduced pressure to remove the 1,2-dichloroethane solvent, yielding the chlorinated intermediate.

[0037] (2) Fluorination reaction

[0038] The chlorinated intermediate was added to a 1000 mL three-necked flask, followed by 500 mL of acetonitrile solvent. The mixture was stirred and the temperature was controlled at 30 °C. 18.5 g (0.5 mol) of ammonium fluoride was added in portions, and the reaction was allowed to proceed for 3 h to obtain a fluorinated reaction solution. The solid salt in the fluorinated reaction solution was filtered out through a Buchner funnel. The resulting filtrate was then dehydrated using a 4A molecular sieve until the water content was <50 ppm. The filtrate was then concentrated under reduced pressure to remove the acetonitrile solvent, yielding a crude liquid product.

[0039] (3) Purification

[0040] The crude liquid product was subjected to vacuum distillation at a vacuum level of 50 Pa, and 54.3 g of liquid with a gas chromatographic purity of 99.2% was collected.

[0041] As an optional embodiment of the present invention, additive A-2 The preparation method is as follows:

[0042] (1) Esterification reaction

[0043] 76.7 g (0.5 mol) of phosphorus oxychloride and 153.4 g of 1,2-dichloroethane solvent were added to a 500 mL three-necked flask. The mixture was stirred and cooled to 15 °C. 30.0 g (0.5 mol) of n-propanol was added dropwise over 30 min. Then, 35.5 g (0.5 mol) of 3-hydroxypropionitrile was added dropwise. After the addition of the starting materials was complete, the temperature was raised to 25 °C, and the reaction was continued for 90 min to obtain a reaction solution containing a chlorinated intermediate. The reaction solution was transferred to a 500 mL single-necked flask and concentrated under reduced pressure to remove the 1,2-dichloroethane solvent, yielding the chlorinated intermediate.

[0044] (2) Fluorination reaction

[0045] The chlorinated intermediate was added to a 1000 mL three-necked flask, followed by 500 mL of acetonitrile solvent. The mixture was stirred and the temperature was controlled at 40 °C. 29.0 g (0.5 mol) of potassium fluoride was added in portions, and the reaction was allowed to proceed for 3 h to obtain a fluorinated reaction solution. The solid salt in the fluorinated reaction solution was filtered out using a Buchner funnel. The resulting filtrate was then dehydrated using a 4A molecular sieve until the water content was <50 ppm. The filtrate was then concentrated under reduced pressure to remove the acetonitrile solvent, yielding a crude liquid product.

[0046] (3) Purification

[0047] The crude liquid product was subjected to vacuum distillation at a vacuum level of 50 Pa, and 87.8 g of liquid with a gas chromatographic purity of 99.4% was collected.

[0048] As an optional embodiment of the present invention, additive A-3 The preparation method is as follows:

[0049] (1) Esterification reaction

[0050] 76.7 g (0.5 mol) of phosphorus oxychloride and 153.4 g of 1,2-dichloroethane solvent were added to a 500 mL three-necked flask. The mixture was stirred and cooled to 15 °C. 23.0 g (0.5 mol) of ethanol was added dropwise over 30 min. Then, 28.5 g (0.5 mol) of hydroxyacetonitrile was added dropwise. After the addition of the starting materials was complete, the temperature was raised to 25 °C, and the reaction was continued for 90 min to obtain a reaction solution containing a chlorinated intermediate. The reaction solution was transferred to a 500 mL single-necked flask and concentrated under reduced pressure to remove the 1,2-dichloroethane solvent, yielding the chlorinated intermediate.

[0051] (2) Fluorination reaction

[0052] The chlorinated intermediate was added to a 1000 mL three-necked flask, followed by 500 mL of acetonitrile solvent. The mixture was stirred and the temperature was controlled at 30 °C. 18.5 g (0.5 mol) of ammonium fluoride was added in portions, and the reaction was allowed to proceed for 3 h to obtain a fluorinated reaction solution. The solid salt in the fluorinated reaction solution was filtered out through a Buchner funnel. The resulting filtrate was then dehydrated using a 4A molecular sieve until the water content was <50 ppm. The filtrate was then concentrated under reduced pressure to remove the acetonitrile solvent, yielding a crude liquid product.

[0053] (3) Purification

[0054] The crude liquid product was subjected to vacuum distillation at a vacuum level of 50 Pa, and 43.4 g of liquid with a gas chromatographic purity of 99.1% was collected.

[0055] For the preparation method of additive A with other structures, refer to the above three preparation methods and adjust the selection of R1 and R2.

[0056] As an optional embodiment of the present invention, the additive B comprises at least one of the compounds having the following structures:

[0057]

[0058]

[0059]

[0060] As an optional embodiment of the present invention, additive B has the structure shown in Formula II. Its preparation method is as follows:

[0061] Esterification reaction is carried out, and the product is purified to obtain additive B. R3 and R4 are each independently selected from alkyl groups with 1-6 carbon atoms, fluoroalkyl groups with 1-6 carbon atoms, or cycloalkyl groups with 3-6 carbon atoms.

[0062] As an optional embodiment of the present invention, additive B-1 The preparation method is as follows:

[0063] (1) Esterification reaction

[0064] 7.1 g (0.1 mol) of 3-hydroxypropionitrile, 10.6 g (0.105 mol) of triethylamine (used as a base), and 100 g of 1,2-dichloroethane solvent were added to a 500 mL three-necked flask and cooled to 0 °C. 15.0 g (0.5 mol, 95% purity) of 2-chloro-2-oxo-1,3,2-dioxophosphazenecyclopentane was dissolved in 50 g of 1,2-dichloroethane solvent and added dropwise to the aforementioned three-necked flask over 2 hours. After the addition of the raw materials was complete, the temperature was raised to 25 °C, and the reaction was continued for 1 hour to obtain the esterification reaction solution. The esterification reaction solution was filtered through a Buchner funnel to remove triethylamine hydrochloride. The resulting filtrate was transferred to a 500 mL single-necked flask and concentrated under reduced pressure to remove the 1,2-dichloroethane solvent, yielding a crude liquid product.

[0065] (2) Purification

[0066] The crude liquid product was subjected to vacuum distillation at a vacuum level of 10 Pa, and 7.1 g of liquid with a gas chromatographic purity of 99.3% was collected.

[0067] As an optional embodiment of the present invention, additive B-2 The preparation method is as follows:

[0068] (1) Esterification reaction

[0069] 7.1 g (0.1 mol) of 3-hydroxypropionitrile, 10.6 g (0.105 mol) of triethylamine (used as a base), and 100 g of 1,2-dichloroethane solvent were added to a 500 mL three-necked flask and cooled to 0 °C. 15.7 g (0.5 mol) of 2-chloro-2-oxo-1,3,2-dioxophosphazenecyclohexane was dissolved in 50 g of 1,2-dichloroethane solvent and added dropwise to the aforementioned three-necked flask over 2 hours. After the addition of the raw materials was complete, the temperature was raised to 25 °C, and the reaction was continued for 1 hour to obtain the esterification reaction solution. The esterification reaction solution was filtered through a Buchner funnel to remove triethylamine hydrochloride. The resulting filtrate was transferred to a 500 mL single-necked flask and concentrated under reduced pressure to remove the 1,2-dichloroethane solvent, yielding a crude liquid product.

[0070] (2) Purification

[0071] The crude liquid product was subjected to vacuum distillation at a vacuum degree of 5 Pa, and 10.5 g of liquid with a gas chromatographic purity of 99.5% was collected.

[0072] For the preparation method of additive B with other structures, refer to the two preparation methods mentioned above and adjust the selection of R3 and R4.

[0073] As an optional embodiment of the present invention, the tricyano compound includes at least one of the following compounds having the following structures:

[0074]

[0075]

[0076] In a second aspect, the present invention provides an electrolyte for an electrochemical energy storage unit, comprising an electrolyte salt, an additive, and an organic solvent, wherein the additive comprises the electrolyte additive combination described in the first aspect.

[0077] As an optional embodiment of the present invention, the electrochemical energy storage unit is a lithium-ion battery or a sodium-ion battery.

[0078] As an optional embodiment of the present invention, the electrochemical energy storage unit is a lithium-ion battery.

[0079] This invention provides an electrolyte additive combination comprising a monocyano compound and a tricyano compound, wherein the monocyano compound is selected from additive A and / or additive B. Additive A is a chain phosphate ester containing one cyano group, and additive B is a cyclic phosphate ester containing one cyano group. In terms of molecular structure design, additives A and B innovatively combine cyano and phosphate groups. Both additives A and B exhibit good oxidation stability, and both the cyano and phosphate groups form complexes with positive electrode metal ions, effectively protecting the positive electrode and reducing the dissolution of positive electrode metal ions under high temperature and high voltage. Both additives A and B can form a phosphorus-based compound protective film on the negative electrode, suppressing impedance growth during battery cycling and improving room temperature cycling performance. The tricyano compound exhibits excellent oxidation stability, and the cyano group forms a complex with positive electrode metal ions, effectively protecting the positive electrode. Experiments have shown that the combination of the monocyano compound and the tricyano compound can exert a synergistic effect, effectively improving the battery's high-temperature storage performance and high-temperature cycling performance, and reducing the amount of cobalt dissolved from the negative electrode.

[0080] As an optional embodiment of the present invention, the mass fraction of additive A in the electrolyte is 0.2%-3%. If the mass fraction of additive A is too high (above 3%), it can easily lead to deterioration of kinetic performance, such as accelerated decay of room temperature cycling performance. If the mass fraction of additive A is too low (below 0.2%), it can easily lead to ineffective addition. Therefore, typical but non-limiting mass fractions of additive A are 0.2%, 0.3%, 0.5%, 0.6%, 0.8%, 1.0%, 1.2%, 1.3%, 1.5%, 1.6%, 1.8%, 2.0%, 2.2%, 2.3%, 2.5%, 2.6%, 2.8%, or 3.0%, as well as numerical ranges between any two points.

[0081] As an optional embodiment of the present invention, the mass fraction of additive B in the electrolyte is 0.2%-3%. If the mass fraction of additive B is too high (above 3%), it can easily lead to deterioration of kinetic performance, such as accelerated decay of room temperature cycling performance. If the mass fraction of additive B is too low (below 0.2%), it can easily lead to ineffective addition. Therefore, typical but non-limiting mass fractions of additive B are 0.2%, 0.3%, 0.5%, 0.6%, 0.8%, 1.0%, 1.2%, 1.3%, 1.5%, 1.6%, 1.8%, 2.0%, 2.2%, 2.3%, 2.5%, 2.6%, 2.8%, or 3.0%, as well as numerical ranges between any two points.

[0082] As an optional embodiment of the present invention, the additive further includes additive C. The main function of additive C is to improve the stability of the electrolyte and electrode interface, thereby enhancing the battery's storage performance and cycle performance. Additive C includes at least one of the following: vinylene carbonate, fluoroethylene carbonate, ethylene ethylene carbonate, lithium bis(oxalato)borate, lithium difluorooxalato)borate, lithium difluorophosphate, lithium tetrafluoroborate, methanedisulfonate, 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, butenyl glycol derivative, tris(trimethylsilane) phosphate, tris(trimethylsilane) borate, vinyl sulfate, propylene sulfate, vinyl sulfite, or tetravinylsilane.

[0083] In a preferred embodiment of the present invention, additive C comprises fluoroethylene carbonate and 1,3-propanesulfonate lactone, wherein the mass ratio of fluoroethylene carbonate to 1,3-propanesulfonate lactone is 10:3.

[0084] In a preferred embodiment of the present invention, additive C comprises fluoroethylene carbonate, 1,3-propanesulfonate lactone, and lithium difluorooxalate borate, wherein the mass ratio of fluoroethylene carbonate, 1,3-propanesulfonate lactone, and lithium difluorooxalate borate is 10:3:0.5.

[0085] In a preferred embodiment of the present invention, additive C is fluoroethylene carbonate.

[0086] In a preferred embodiment of the present invention, additive C is 1,3-propanesulfonate lactone.

[0087] In a preferred embodiment of the present invention, additive C is methylene methane disulfonate.

[0088] As an optional embodiment of the present invention, the additive C has a mass fraction of 1%-15% in the electrolyte. Typical but non-limiting mass fractions are 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%, and numerical ranges between any two points.

[0089] As an optional embodiment of the present invention, the electrolyte salt includes at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, sodium hexafluorophosphate, sodium bis(fluorosulfonyl)imide, or sodium bis(trifluoromethanesulfonyl)imide.

[0090] As an optional embodiment of the present invention, the concentration of the electrolyte salt in the electrolyte is 0.6 mol / L-1.8 mol / L, and typical but non-limiting concentrations are 0.6 mol / L, 0.8 mol / L, 1.0 mol / L, 1.2 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L or 1.8 mol / L, and any numerical range between any two points.

[0091] As an optional embodiment of the present invention, the organic solvent includes at least three of the following: dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, propyl propionate, propyl acetate, ethyl propionate, ethyl acetate, or 2,2-difluoroethyl acetate.

[0092] As an optional embodiment of the present invention, the organic solvent includes ethylene carbonate, propylene carbonate, ethyl propionate, and propyl propionate, wherein the mass ratio of ethylene carbonate, propylene carbonate, ethyl propionate, and propyl propionate is 15:15:20:50.

[0093] Thirdly, the present invention provides an electrochemical energy storage unit, comprising the electrolyte additive combination described in the first aspect or the electrolyte for an electrochemical energy storage unit described in the second aspect.

[0094] As an optional embodiment of the present invention, the electrochemical energy storage unit is a lithium-ion battery or a sodium-ion battery.

[0095] As an optional embodiment of the present invention, the electrochemical energy storage unit is a lithium-ion battery, and the lithium-ion battery further includes a positive electrode, a negative electrode, and a separator between the positive electrode and the negative electrode.

[0096] As an optional embodiment of the present invention, the positive electrode active material includes at least one of nickel-cobalt-manganese ternary materials, nickel-cobalt-aluminum ternary materials, or lithium cobalt oxide.

[0097] As an optional embodiment of the present invention, the negative electrode active material includes at least one of natural graphite, artificial graphite, silicon, silicon alloy, silicon-carbon, or silicon-oxygen.

[0098] Fourthly, the present invention provides a power device comprising the electrolyte additive combination described in the first aspect, the electrolyte for the electrochemical energy storage unit described in the second aspect, or the electrochemical energy storage unit described in the third aspect.

[0099] As an optional embodiment of the present invention, the power unit includes at least one of electric vehicles, electric ships, electric aircraft, or power tools. Electric vehicles include electric cars, electric buses, electric trams, electric bicycles, electric motorcycles, electric scooters, electric golf carts, and electric trucks, etc. Electric vehicles include pure electric vehicles or hybrid electric vehicles; hybrid electric vehicles can be plug-in hybrid electric vehicles. Electric ships include ferries, passenger ships, tugboats, and sightseeing boats, etc. Electric aircraft include electric airplanes, electric helicopters, electric gliders, and electric drones, etc. Power tools include electric drills, impact drills, electric hammers, electric saws, electric cutters, electric lawnmowers, electric vacuum cleaners, and electric mixers, etc.

[0100] Fifthly, the present invention provides an energy storage device, comprising the electrolyte additive combination described in the first aspect, the electrolyte for an electrochemical energy storage unit described in the second aspect, or the electrochemical energy storage unit described in the third aspect.

[0101] As an optional embodiment of the present invention, the energy storage device is a communication base station or grid energy storage, etc.

[0102] Compared with the prior art, the present invention has the following beneficial effects:

[0103] This invention provides an electrolyte additive combination comprising a monocyano compound and a tricyano compound, wherein the monocyano compound is selected from additive A and / or additive B. Additive A is a chain phosphate ester containing one cyano group, and additive B is a cyclic phosphate ester containing one cyano group. In terms of molecular structure design, additives A and B innovatively combine cyano and phosphate groups. Both additives A and B exhibit good oxidation stability. When applied to electrochemical energy storage units, both the cyano and phosphate groups form complexes with the positive electrode metal ions, effectively protecting the positive electrode and reducing the dissolution of positive electrode metal ions under high temperature and high voltage. Both additives A and B can form a phosphorus-based compound protective film at the negative electrode, inhibiting impedance growth during cycling and improving room temperature cycling performance. The tricyano compound exhibits excellent oxidation stability. When applied to electrochemical energy storage units, the cyano group forms a complex with the positive electrode metal ions, effectively protecting the positive electrode. Experiments have shown that the combination of the monocyano compound and the tricyano compound can exert a synergistic effect, effectively improving the battery's high-temperature storage performance and high-temperature cycling performance. Detailed Implementation

[0104] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Those skilled in the art should understand that the embodiments described are merely illustrative of the invention and should not be considered as specific limitations thereof. 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. Process parameters not specifically specified in the following embodiments are generally performed under conventional conditions.

[0105] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0106] The present invention will be further described in detail below with reference to specific embodiments and comparative examples. Those skilled in the art should understand that the embodiments are merely illustrative of the invention and should not be considered as specific limitations thereof. Besides additives A and B prepared according to the above method, all other raw materials used in the present invention can be obtained from commercially available products. The specific structures of additives A and B in the following embodiments and comparative examples are shown in Table 1:

[0107] Table 1

[0108]

[0109] Example 1

[0110] This embodiment provides a lithium-ion battery electrolyte, including an electrolyte additive combination, which includes additive A and a tricyano compound; the lithium-ion battery electrolyte specifically includes the following components by mass fraction: electrolyte salt 15%, additive A 2%, tricyano compound 2%, additive C 13%, and the balance being an organic solvent;

[0111] The electrolyte salt is lithium hexafluorophosphate, and its concentration in the electrolyte is 1.2 mol / L.

[0112] Additive A is additive A-1, and its specific structure is shown in Table 1.

[0113] The tricyano compound is 1,3,6-hexanetrionitrile (HTCN);

[0114] Additive C includes fluoroethylene carbonate and 1,3-propanesulfonate lactone, with a mass ratio of fluoroethylene carbonate and 1,3-propanesulfonate lactone of 10:3.

[0115] The organic solvents include ethylene carbonate, propylene carbonate, ethyl propionate, and propyl propionate. The mass ratio of ethylene carbonate, propylene carbonate, ethyl propionate, and propyl propionate is 15:15:20:50, based on the total mass of the organic solvents as 100%.

[0116] The method for preparing the lithium-ion battery electrolyte in this embodiment includes the following steps:

[0117] Ethyl carbonate, propylene carbonate, ethyl propionate, and propyl propionate are mixed in a certain proportion to form an organic solvent. Then, an electrolyte salt (lithium hexafluorophosphate) is added to the organic solvent in the prescribed amount. Additive C (fluoroethylene carbonate and 1,3-propanesulfonate lactone) is added in the prescribed amount, followed by additive A and tricyano compound. The mixture is then stirred evenly to obtain a lithium-ion battery electrolyte.

[0118] Example 2

[0119] This embodiment provides a lithium-ion battery electrolyte, except that additive A-1 is replaced with additive A-2, and the other raw materials and amounts are the same as in Example 1.

[0120] The structural formula of additive A-2 is shown in Table 1.

[0121] Example 3

[0122] This embodiment provides a lithium-ion battery electrolyte, except that additive A-1 is replaced with additive A-3, and the other raw materials and amounts are the same as in Example 1.

[0123] The structural formula of additive A-3 is shown in Table 1.

[0124] Example 4

[0125] This embodiment provides a lithium-ion battery electrolyte, except that the mass fraction of additive A-1 is adjusted from 2% to 0.2%, while the other raw materials and amounts are the same as in Example 1.

[0126] Example 5

[0127] This embodiment provides a lithium-ion battery electrolyte, except that the mass fraction of additive A-1 is adjusted from 2% to 1%, while the other raw materials and amounts are the same as in Example 1.

[0128] Example 6

[0129] This embodiment provides a lithium-ion battery electrolyte, except that the mass fraction of additive A-1 is adjusted from 2% to 3%, while the other raw materials and amounts are the same as in Example 1.

[0130] Example 7

[0131] This embodiment provides a lithium-ion battery electrolyte, except that additive A-1 is replaced with additive B-1, and the other raw materials and amounts are the same as in Example 1.

[0132] The structural formula of additive B-1 is shown in Table 1.

[0133] Example 8

[0134] This embodiment provides a lithium-ion battery electrolyte, except that 2% by mass of additive A-1 is replaced with 1% by mass of additive B-1, while the other raw materials and amounts are the same as in Example 1.

[0135] Example 9

[0136] This embodiment provides a lithium-ion battery electrolyte, except that 2% by mass of additive A-1 is replaced with 3% by mass of additive B-1, while the other raw materials and amounts are the same as in Example 1.

[0137] Example 10

[0138] This embodiment provides a lithium-ion battery electrolyte, except that additive A-1 is replaced with additive B-2, and the other raw materials and amounts are the same as in Example 1.

[0139] The structural formula of additive B-2 is shown in Table 1.

[0140] Example 11

[0141] This embodiment provides a lithium-ion battery electrolyte, except that 2% by mass of additive A-1 is replaced with 1% by mass of additive A-1 and 1% by mass of additive B-1, while the other raw materials and amounts are the same as in Example 1.

[0142] Example 12

[0143] This embodiment provides a lithium-ion battery electrolyte, except that the mass fraction of additive A-1 is adjusted from 2% to 3%, and the mass fraction of tricyano compound HTCN is adjusted from 2% to 3%, while the other raw materials and their amounts are the same as in Example 1.

[0144] Example 13

[0145] This embodiment provides a lithium-ion battery electrolyte, except that 2% by mass of the tricyano compound HTCN is replaced with 3% by mass of 1,2,3-tris(2-cyanoethoxy)propane, and the other raw materials and amounts are the same as in Example 1.

[0146] Example 14

[0147] This embodiment provides a lithium-ion battery electrolyte, except that 2% by mass of the tricyano compound HTCN is replaced with 3% by mass of 1,3,5-cyclohexanetrionitrile, while the other raw materials and amounts are the same as in Example 1.

[0148] Example 15

[0149] This embodiment provides a lithium-ion battery electrolyte, except that 2% by mass of the tricyano compound HTCN is replaced with 4% by mass of 1,3,5-pentanetricarbonyl nitrile, while the other raw materials and amounts are the same as in Example 1.

[0150] Example 16

[0151] This embodiment provides a lithium-ion battery electrolyte, except that the mass fraction of additive C is adjusted from 13% to 13.5%, and the composition of additive C is adjusted as follows: additive C includes fluoroethylene carbonate, 1,3-propanesulfonate lactone and lithium difluorooxalate borate, and the mass ratio of fluoroethylene carbonate, 1,3-propanesulfonate lactone and lithium difluorooxalate borate is 10:3:0.5; the remaining raw materials and their amounts are the same as in Example 1.

[0152] Example 17

[0153] This embodiment provides a lithium-ion battery electrolyte, except that the mass fraction of additive C is adjusted from 13% to 10%, and the composition of additive C is adjusted to include fluoroethylene carbonate; the remaining raw materials and their amounts are the same as in Example 1.

[0154] Example 18

[0155] This embodiment provides a lithium-ion battery electrolyte, except that the mass fraction of additive C is adjusted from 13% to 3%, and the composition of additive C is adjusted as follows: additive C includes 1,3-propanesulfonate lactone, and the remaining raw materials and amounts are the same as in Example 1.

[0156] Example 19

[0157] This embodiment provides a lithium-ion battery electrolyte, except that the mass fraction of additive C is adjusted from 13% to 1%, and the composition of additive C is adjusted to include methylene methane disulfonate. The remaining raw materials and their amounts are the same as in Example 1.

[0158] Example 20

[0159] This embodiment provides a lithium-ion battery electrolyte that is identical to that of Example 1 except that it does not contain additive C.

[0160] Comparative Example 1

[0161] This comparative example provides a lithium-ion battery electrolyte, which is identical to that of Example 1 except that additive A-1 and tricyano compound HTCN are not added.

[0162] Comparative Example 2

[0163] This comparative example provides a lithium-ion battery electrolyte, which is the same as that in Example 1 except that the tricyano compound HTCN is not added.

[0164] Comparative Example 3

[0165] This comparative example provides a lithium-ion battery electrolyte, which is identical to that of Example 1 except that additive A-1 is not added.

[0166] Comparative Example 4

[0167] This comparative example provides a lithium-ion battery electrolyte, except that additive A-1 is replaced with succinate SN, and the other raw materials and amounts are the same as in Example 1.

[0168] Comparative Example 5

[0169] This comparative example provides a lithium-ion battery electrolyte, except that 2% by mass of additive A-1 is replaced with 1% by mass of succinate SN and 2% by mass of adiponitrile ADN, and the remaining raw materials and amounts are the same as in Example 1.

[0170] Comparative Example 6

[0171] This comparative example provides a lithium-ion battery electrolyte, except that the mass fraction of additive A-1 is adjusted from 2% to 0.05%, while the other raw materials and amounts are the same as in Example 1.

[0172] Comparative Example 7

[0173] This comparative example provides a lithium-ion battery electrolyte, except that the mass fraction of additive A-1 is adjusted from 2% to 3.5%, while the other raw materials and amounts are the same as in Example 1.

[0174] Comparative Example 8

[0175] This comparative example provides a lithium-ion battery electrolyte, except that the mass fraction of the tricyano compound HTCN is adjusted from 2% to 4.5%, while the other raw materials and amounts are the same as in Example 1.

[0176] Application Example 1-20 and Comparative Application Example 1-8

[0177] The lithium-ion battery electrolytes obtained in Examples 1-20 and Comparative Examples 1-8 were used to prepare lithium-ion battery application examples 1-20 and comparative application examples 1-8 (i.e., the lithium-ion battery electrolyte of Example 1 was used to prepare lithium-ion battery application example 1, the lithium-ion battery electrolyte of Example 2 was used to prepare lithium-ion battery application example 2, the lithium-ion battery electrolyte of Comparative Example 1 was used to prepare lithium-ion battery comparative application example 1, the lithium-ion battery electrolyte of Comparative Example 4 was used to prepare lithium-ion battery comparative application example 4, and so on). The specific preparation methods are as follows:

[0178] Preparation of the positive electrode sheet: The positive electrode active material lithium cobalt oxide LB08 (Xiamen Tungsten New Energy Materials Co., Ltd.), conductive agent carbon black (SP), conductive agent carbon nanotubes (CNT), and binder polyvinylidene fluoride (PVDF) are thoroughly mixed in N-methylpyrrolidone (NMP) solvent at a weight ratio of 97.075:1.0:0.625:1.3 to form a uniform positive electrode slurry. This slurry is then coated onto the positive electrode current collector aluminum foil, dried, and cold-pressed to achieve a double-sided surface density of 355 g / m². 2 Compacted density 4.0 g / cm³ 3 A positive electrode sheet with a specific capacity of 195mAh / g was obtained.

[0179] Fabrication of the negative electrode sheet: The negative electrode active material, artificial graphite QCG-H2 (Shanghai Shanshan Technology Co., Ltd.), silicon carbide CONE-LSC-2 (Zhejiang Lichen New Material Technology Co., Ltd.), conductive agent carbon black (SP), thickener sodium carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber are thoroughly mixed in a deionized water solvent at a mass ratio of 91.5:5:0.5:1.4:1.6 to form a uniform negative electrode slurry. This slurry is then coated onto the negative electrode current collector copper foil, dried, and cold-pressed to achieve a double-sided surface density of 160 g / m³. 2 Compacted density 1.6 g / cm³ 3 A negative electrode sheet with a specific capacity of 420mAh / g was obtained.

[0180] The positive electrode, PE separator (Shenzhen Xingyuan Material Technology Co., Ltd.), and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes for isolation. Then, they are wound to obtain a bare battery cell. The bare battery cell is placed in an outer packaging bag, and electrolyte is injected into the dried battery. After vacuum sealing, settling, formation, and shaping processes, a lithium-ion battery with a nominal capacity of 1500mAh is obtained.

[0181] Test conditions

[0182] The electrochemical performance of the lithium-ion batteries prepared in Application Examples 1-20 and Comparative Application Examples 1-8 was tested using the following methods:

[0183] 1. Store at 85℃ for 8 hours to reach 100% SOC (100% SOC means fully charged).

[0184] (1) Discharge the battery at 0.2C to 3.0V and let it stand for 10 minutes;

[0185] (2) Charge to 4.53V using 0.5C CC-CV (constant current and constant voltage), cut off current 1 / 20C, and let stand for 10 minutes;

[0186] (3) Discharge at 0.5C to 3.0V and let stand for 10 minutes;

[0187] Repeat (2)-(3) twice and record the second discharge capacity Q1;

[0188] (4) Charge the battery to 4.53V using a 0.5C CC-CV (constant current and constant voltage) circuit, cut off the current at 1 / 20C, and measure the internal resistance (denoted as R5), voltage (denoted as U1), volume (denoted as V1), and thickness (denoted as H1).

[0189] (5) Let stand at 85℃ for 8 hours;

[0190] (6) Measure the internal resistance (denoted as R6), voltage (denoted as U2), volume (denoted as V2), and thickness (denoted as H2) under hot conditions;

[0191] (7) At 25℃, let stand for 2 hours, and measure the thickness at room temperature and record it as H3;

[0192] (8) Discharge at 0.5C to 3.0V, let stand for 10 minutes, and record the capacity Q2;

[0193] (9) Charge to 4.53V using 0.5C CC-CV (constant current and constant voltage), cut off current 1 / 20C, and let stand for 10 minutes;

[0194] (10) Discharge at 0.5C to 3.0V and let stand for 10 minutes;

[0195] (11) Repeat steps (9)-(10) twice, and record the capacity Q3 and Q4;

[0196] Capacity retention rate = Q2 / Q1; Capacity recovery rate = max(Q3:Q4) / Q1, where max(Q3:Q4) refers to taking the maximum value between the capacities Q3 and Q4;

[0197] Volume change rate = V2 / V1; Voltage change rate = U2 / U1; Internal resistance change rate = R6 / R5;

[0198] The test data are shown in Table 2.

[0199] 2. Test of cobalt leaching from negative electrode

[0200] After the battery has completed the 85℃ high-temperature storage test, discharge it to 3.0V and test it according to the following steps:

[0201] (1) Disassemble the battery inside the glove box and cut off a negative electrode sheet of a certain area;

[0202] (2) Place the above negative electrode sheets into the PFA digestion vessel, weigh them with an analytical balance, and record the sample mass;

[0203] (3) Add 5 mL of ultrapure water to the weighed PFA digestion vessel, then add 7 mL of nitric acid, tighten the lid, and place the PFA digestion vessel into the graphite digestion furnace for digestion at 150°C for 3 hours.

[0204] (4) After digestion, remove the PFA digestion vessel from the graphite furnace digester and cool it. Then filter the cooled digestion solution into a 50mL plastic volumetric flask using a glass funnel with quantitative filter paper. The inner wall of the PFA digestion vessel should also be rinsed with ultrapure water into a glass funnel with quantitative filter paper. Then make up to volume with ultrapure water, shake well and dilute 10 times for testing.

[0205] (5) Dilute the mixed standard containing elements such as Ni, Co, and Mn with 2% nitric acid to a gradient of 0 mg / L, 0.05 mg / L, 0.10 mg / L, 0.20 mg / L, 0.50 mg / L, and 1.00 mg / L, and test it using ICP-OES.

[0206] (6) Calculate the cobalt content in the sample, i.e., the amount of cobalt leached from the negative electrode, based on the results of the machine reading test. Take two negative electrode sheets for parallel testing each time and take the average value.

[0207] The test data are shown in Table 2.

[0208] 3. 45℃ Cyclic Test

[0209] (1) Let stand at 45℃ for 2 hours;

[0210] (2) Discharge at 0.5C to 3.0V and let stand for 10 minutes;

[0211] (3) Charge to 4.53V using 0.5C CC-CV (constant current and constant voltage), cut off current 1 / 20C, and let stand for 10 minutes;

[0212] (4) Discharge at 0.7C to 3.0V and let stand for 10 minutes;

[0213] (5) Repeat steps (3)-(4) for 300 cycles.

[0214] The 300-cycle capacity retention rate was calculated using the 300-cycle capacity and the initial capacity, and the test data are shown in Table 3.

[0215] 4. 25℃ Cyclic Test

[0216] (1) Let stand at 25℃ for 2 hours;

[0217] (2) Discharge at 0.5C to 3.0V and let stand for 10 minutes;

[0218] (3) Charge to 4.53V using 0.7C CC-CV (constant current and constant voltage), cut off current 1 / 20C, and let stand for 10 minutes;

[0219] (4) Discharge to 3.0V at 1C and let stand for 10 minutes;

[0220] (5) Repeat steps (3)-(4) for 500 cycles.

[0221] The 500-cycle capacity retention rate was calculated using the 500-cycle capacity and the initial capacity, and the test data are shown in Table 3.

[0222] Table 2

[0223]

[0224]

[0225] Table 3

[0226]

[0227]

[0228] As can be seen from the data in Tables 2 and 3, the electrochemical performance of lithium-ion batteries (Application Examples 1-20) prepared using the lithium-ion battery electrolytes provided in the various embodiments of the present invention is significantly higher than that of lithium-ion batteries (Comparative Application Examples 1-8) prepared using the comparative lithium-ion battery electrolytes.

[0229] Specifically, Comparative Application Examples 1-3 are comparative experiments of Application Example 1, mainly examining the effect of adding monocyano compounds and / or tricyano compounds on battery performance. As can be seen from the experimental data of Application Example 1 and Comparative Application Examples 1-3 in Tables 2-3, the simultaneous addition of monocyano compounds and tricyano compounds significantly improves the battery's high-temperature storage performance and high-temperature cycle performance, and reduces the amount of cobalt dissolved from the negative electrode. Furthermore, the battery's room-temperature cycle performance is slightly better or comparable, whereas adding either monocyano compound or tricyano compound alone does not achieve such significant effects.

[0230] Comparative Application Examples 4-5 are also comparative experiments with Application Example 1, mainly examining the effect of the combination of dicyano and tricyano compounds on battery performance. Data from Tables 2-3 show that the addition of the dicyano and tricyano compound combination significantly reduces various aspects of battery performance. This demonstrates a synergistic relationship between the monocyano and tricyano compounds in this invention; only through their combined action can the battery's high-temperature storage and cycling performance be significantly improved, and the amount of cobalt leached from the negative electrode reduced. Furthermore, the battery's room-temperature cycling performance is slightly better or comparable.

[0231] Comparative Application Examples 6-8 are also comparative experiments of Application Example 1, mainly examining the effect of the amount of monocyano compound or tricyano compound used. As can be seen from the relevant experimental data in Table 2-3, excessive addition of monocyano compound or tricyano compound affects battery performance, while insufficient addition fails to achieve the desired effect.

[0232] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention shall be within the scope of protection of the pending claims of the present invention.

Claims

1. An electrolyte additive combination, characterized in that, The electrolyte additive combination includes a monocyano compound and a tricyano compound, wherein the monocyano compound is selected from additive A and / or additive B, wherein the structure of additive A is shown in Formula I and the structure of additive B is shown in Formula II. In Formula I, R1 and R2 are each independently selected from alkyl groups having 1-6 carbon atoms, fluoroalkyl groups having 1-6 carbon atoms, or cycloalkyl groups having 3-6 carbon atoms; In Formula II, R3 and R4 are each independently selected from alkyl groups having 1-6 carbon atoms, fluoroalkyl groups having 1-6 carbon atoms, or cycloalkyl groups having 3-6 carbon atoms; The tricyano compound includes at least one of the following compounds having the following structure: The mass ratio of the monocyano compound to the tricyano compound is (0.2-3):(0.2-4).

2. The electrolyte additive combination according to claim 1, characterized in that, R1 is selected from alkyl groups having 1-4 carbon atoms or fluoroalkyl groups having 1-4 carbon atoms.

3. The electrolyte additive combination according to claim 1, characterized in that, R2 is selected from alkyl groups having 1-4 carbon atoms, fluoroalkyl groups having 1-4 carbon atoms, or cycloalkyl groups having 3-6 carbon atoms.

4. The electrolyte additive combination according to claim 1, characterized in that, R3 is selected from alkyl groups having 1-4 carbon atoms, fluoroalkyl groups having 1-4 carbon atoms, or cycloalkyl groups having 3-6 carbon atoms.

5. The electrolyte additive combination according to claim 1, characterized in that, R4 is selected from alkyl groups having 1-4 carbon atoms or fluoroalkyl groups having 1-4 carbon atoms.

6. The electrolyte additive combination according to claim 1, characterized in that, R1, R2, R3, and R4 are each independently selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, tert-pentyl, n-hexyl, 2-fluoroethyl, 2,2-difluoroethyl, 1,2-difluoroethyl, 2,2,2-trifluoroethyl, 1-fluoropropyl, 2-fluoropropyl, 2,2-difluoropropyl, 1,3-difluoropropyl, 3,3,3-trifluoropropyl, 2,2,3,3-tetrafluoropropyl, 2,2,3,3,3-pentafluoropropyl, 4-fluorobutyl, 4,4,4-trifluorobutyl, 3,3,4,4,4-pentafluorobutyl, or 2,2,3,3,tetrafluorobutyl.

7. The electrolyte additive combination according to any one of claims 1-6, characterized in that, The additive A comprises at least one of the following compounds having the following structures:

8. The electrolyte additive combination according to any one of claims 1-6, characterized in that, The additive B comprises at least one of the following compounds having the following structures:

9. An electrolyte for an electrochemical energy storage unit, characterized in that, It includes electrolyte salts, additives, and organic solvents, wherein the additives include the electrolyte additive combination as described in any one of claims 1-8.

10. The electrolyte for an electrochemical energy storage unit according to claim 9, characterized in that, The electrochemical energy storage unit is a lithium-ion battery or a sodium-ion battery.

11. The electrolyte for an electrochemical energy storage unit according to claim 9, characterized in that, The additive A has a mass fraction of 0.2%-3% in the electrolyte.

12. The electrolyte for an electrochemical energy storage unit according to claim 9, characterized in that, The additive B has a mass fraction of 0.2%-3% in the electrolyte.

13. The electrolyte for an electrochemical energy storage unit according to any one of claims 9-12, characterized in that, The additive further includes additive C, which comprises at least one of vinylene carbonate, fluoroethylene carbonate, ethylene ethylene carbonate, lithium bis(oxalato)borate, lithium difluorooxalato)borate, lithium difluorophosphate, lithium tetrafluoroborate, methanedisulfonate, 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, butene glycol derivative, tris(trimethylsilane) phosphate, tris(trimethylsilane) borate, vinyl sulfate, propylene sulfate, vinyl sulfite, or tetravinylsilane.

14. The electrolyte for an electrochemical energy storage unit according to claim 13, characterized in that, The additive C has a mass fraction of 1%-15% in the electrolyte.

15. The electrolyte for an electrochemical energy storage unit according to any one of claims 9-12, characterized in that, The electrolyte salt includes at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, sodium hexafluorophosphate, sodium bis(fluorosulfonyl)imide, or sodium bis(trifluoromethanesulfonyl)imide.

16. The electrolyte for an electrochemical energy storage unit according to any one of claims 9-12, characterized in that, The concentration of the electrolyte salt in the electrolyte is 0.6 mol / L-1.8 mol / L.

17. The electrolyte for an electrochemical energy storage unit according to any one of claims 9-12, characterized in that, The organic solvent includes at least three of the following: dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, propyl propionate, propyl acetate, ethyl propionate, ethyl acetate, or 2,2-difluoroethyl acetate.

18. An electrochemical energy storage unit, characterized in that, Includes the electrolyte additive combination as described in any one of claims 1-8 or the electrolyte for electrochemical energy storage units as described in any one of claims 9-17.

19. The electrochemical energy storage unit according to claim 18, characterized in that, The electrochemical energy storage unit is a lithium-ion battery or a sodium-ion battery.

20. The electrochemical energy storage unit according to claim 18 or 19, characterized in that, The electrochemical energy storage unit is a lithium-ion battery, and the lithium-ion battery further includes a positive electrode, a negative electrode, and a separator between the positive electrode and the negative electrode.

21. The electrochemical energy storage unit according to claim 20, characterized in that, The positive electrode active material includes at least one of nickel-cobalt-manganese ternary materials, nickel-cobalt-aluminum ternary materials, or lithium cobalt oxide.

22. The electrochemical energy storage unit according to claim 20, characterized in that, The negative electrode active material includes at least one of natural graphite, artificial graphite, silicon, silicon alloy, silicon-carbon, or silicon-oxygen.

23. A power unit, characterized in that, Includes the electrolyte additive combination as described in any one of claims 1-8, the electrolyte for electrochemical energy storage units as described in any one of claims 9-17, or the electrochemical energy storage unit as described in any one of claims 18-22.

24. The power unit according to claim 23, characterized in that, The power unit includes at least one of electric vehicles, electric ships, electric aircraft, or power tools.

25. An energy storage device, characterized in that, Includes the electrolyte additive combination as described in any one of claims 1-8, the electrolyte for electrochemical energy storage units as described in any one of claims 9-17, or the electrochemical energy storage unit as described in any one of claims 18-22.

26. The energy storage device according to claim 25, characterized in that, The energy storage device is a communication base station or grid energy storage.

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