Electrolyte additive combination, electrolyte for electrochemical energy storage unit, and use of electrolyte

Abstract

An electrolyte additive combination, an electrolyte for an electrochemical energy storage unit, and a use of the electrolyte. The electrolyte additive combination comprises a mono-cyano compound and a tricyano compound. The mono-cyano compound is selected from additive A and / or additive B. Both the cyano group and the phosphate group in the additive A or the additive B have a complexation effect with metal ions in a positive electrode, so that the positive electrode can be effectively protected and a phosphorus-based compound protective film can be formed on a negative electrode. The cyano group in the tricyano compound has a complexation effect with the metal ions in the positive electrode, so that the positive electrode can be effectively protected. The combination of the mono-cyano compound and the tricyano compound can play a synergistic role, so that the high-temperature storage performance and high-temperature cycle performance of the battery can be effectively improved.

Description

Electrolyte additive combination, electrolyte for electrochemical energy storage unit and application thereof TECHNICAL FIELD

[0001] The present application belongs to the technical field of electrolyte materials, for example, an electrolyte additive combination, an electrolyte for electrochemical energy storage unit and application thereof. BACKGROUND

[0002] Lithium ion batteries are widely used in consumer electronics, power and energy storage fields. In order to meet the demand of high capacity, developing high voltage lithium battery has become an effective means to improve energy density. The supporting high voltage electrolyte will use a large number of positive electrode protection additives, among which nitrile additives are indispensable components. Specifically, by using a combination of dicyan-based compounds and tricyan-based compounds, good comprehensive performance of the battery can be achieved. However, under the voltage system of 4.53V and above, the combination of dicyan-based compounds and tricyan-based compounds has deficiencies in the high temperature storage and high temperature cycle performance of lithium batteries, which is difficult to meet the application requirements.

[0003] Therefore, it is urgent to develop an electrolyte system to solve the above problems.

[0004] SUMMARY

[0005] The following is a summary of the subject matter of the detailed description herein. This summary is not intended to limit the scope of the claims.

[0006] The present application provides an electrolyte additive combination, an electrolyte for electrochemical energy storage unit and application thereof. The electrolyte additive combination added to the electrolyte can effectively improve the high temperature storage performance of the electrochemical energy storage unit.

[0007] The present application adopts the following technical solutions:

[0008] In a first aspect, the present application provides an electrolyte additive combination, which comprises a monocyano compound and a tricyano compound, the monocyano compound is selected from additive A and / or additive B, the structure of the additive A is shown as formula I, and the structure of the additive B is shown as formula II,

[0009] In formula I, R1 and R2 are each independently selected from alkyl with carbon atom number of 1-6, fluoroalkyl with carbon atom number of 1-6 or cycloalkyl with carbon atom number of 3-6;

[0010] In formula II, R3 and R4 are each independently selected from alkyl with carbon atom number of 1-6, fluoroalkyl with carbon atom number of 1-6 or cycloalkyl with carbon atom number of 3-6.

[0011] The present application regulates the composition of an electrolyte additive combination, the electrolyte additive combination comprising a single-cyano compound and a tri-cyano compound, and the single-cyano compound is selected from Additive A and / or Additive B. The cyano group and the phosphate group in Additive A or Additive B are both complexed with positive metal ions, which can effectively protect the positive electrode and form a phosphorus compound protective film at the negative electrode. The cyano group in the tri-cyano compound is complexed with positive metal ions, which can effectively protect the positive electrode. It is found that the combination of single-cyano compounds and tri-cyano compounds can play a synergistic effect when applied to electrochemical energy storage units, which can effectively improve the high-temperature storage performance and high-temperature cycle performance of the battery.

[0012] In the present application, the carbon atom number range defined by R1, R2, R3 and R4 above refers to any integer within the defined range, the carbon atom number is 1-6, which can be 1, 2, 3, 4, 5 or 6; the carbon atom number is 3-6, which can be 3, 4, 5 or 6; R1, R2, R3 and R4 can be the same or different. The alkyl group can be linear or branched.

[0013] As an optional embodiment of the present application, R1, R2, R3 and R4 are each independently selected from an alkyl group with a carbon atom number of 1-4, a fluoroalkyl group with a carbon atom number of 1-4 or a cycloalkyl group with a carbon atom number of 3-6.

[0014] As an optional embodiment of the present application, R1 is selected from an alkyl group with a carbon atom number of 1-4 or a fluoroalkyl group with a carbon atom number of 1-4.

[0015] As an optional embodiment of the present application, R2 is selected from an alkyl group with a carbon atom number of 1-4, a fluoroalkyl group with a carbon atom number of 1-4 or a cycloalkyl group with a carbon atom number of 3-6.

[0016] As an optional embodiment of the present application, R3 is selected from an alkyl group with a carbon atom number of 1-4, a fluoroalkyl group with a carbon atom number of 1-4 or a cycloalkyl group with a carbon atom number of 3-6.

[0017] As an optional embodiment of the present application, R4 is selected from an alkyl group with a carbon atom number of 1-4 or a fluoroalkyl group with a carbon atom number of 1-4.

[0018] As an optional embodiment of the present application, the alkyl group with a carbon atom number of 1-6 is selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, tert-pentyl or n-hexyl.

[0019] As an optional embodiment of the present application, 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.

[0020] As an optional embodiment of the present application, the cycloalkyl group having 3-6 carbon atoms is selected from cyclopropyl, cyclobutyl, cyclopentyl or cyclohexyl.

[0021] As an optional embodiment of the present application, R1, R2, R3and R4are 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.

[0022] As an optional embodiment of the present application, R1, R2, R3and R4are each independently selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, tert-pentyl or n-hexyl.

[0023] As an optional embodiment of the present application, R1, R2, R3and R4are 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.

[0024] As an optional embodiment of the present application, R1is selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, n-pentyl, isopentyl, tert-pentyl, n-hexyl or 2-fluoropropyl.

[0025] As an optional embodiment of the present application, R2is 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.

[0026] As an optional embodiment of the present application, R3 is selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, n-pentyl, cyclohexyl, 2-fluoroethyl, 2-fluoropropyl or 2,2-difluoropropyl.

[0027] As an optional embodiment of the present application, R4 is selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, n-pentyl, isopentyl, t-pentyl, n-hexyl or 2-fluoropropyl.

[0028] As an optional embodiment of the present application, the mass ratio of the mono-cyano compound and the tri-cyano compound is (0.2-3):(0.2-4). The mono-cyano compound and the tri-cyano compound typically but not limitatively have a mass ratio of 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, 1.5:0.5, 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. By further limiting the mass ratio of the mono-cyano compound and the tri-cyano compound, the synergistic effect between the mono-cyano compound and the tri-cyano compound is enhanced.

[0029] As an optional embodiment of the present application, the additive A comprises at least one of the compounds having the following structure:

[0030] As an optional embodiment of the present application, the additive A has the structure as shown in Formula I, The preparation method is as follows:

[0031] Phosphorus oxychloride, NC-R1-OH and R2-OH are subjected to esterification to obtain an intermediate After fluorination reaction, the additive A is obtained by purification. R1 and R2 are each independently selected from alkyl with carbon number of 1-6, fluoroalkyl with carbon number of 1-6 or cycloalkyl with carbon number of 3-6.

[0032] As an optional embodiment of the present application, the additive A-1 is prepared by the following method:

[0033] (1) esterification reaction

[0034] In a 500 mL three-necked flask, 76.7 g (0.5 mol) of phosphorus oxychloride and 153.4 g of 1,2-dichloroethane solvent are added, and the mixture is stirred and cooled to 15°C. Then 23.0 g (0.5 mol) of ethanol is added dropwise, and the addition is completed within 30 min. Then 35.5 g (0.5 mol) of 3-hydroxypropionitrile is added dropwise. After the addition of the raw materials is completed, the temperature is increased to 25°C, and the reaction is continued for 90 min to obtain a reaction solution containing a chlorinated intermediate. The reaction solution is transferred to a 500 mL single-necked flask, and the 1,2-dichloroethane solvent is removed by concentration under reduced pressure to obtain the chlorinated intermediate.

[0035] (2) fluorination reaction

[0036] In a 1000 mL three-necked flask, the chlorinated intermediate is added, and 500 mL of acetonitrile solvent is added for stirring. The temperature is controlled to 30°C, and 18.5 g (0.5 mol) of ammonium fluoride is added in batches. The reaction is continued for 3 h to obtain a fluorination reaction solution. The solid salt is removed by filtration through a Buchner funnel, and the obtained filtrate is dehydrated to a water content of <50 ppm by passing through 4A molecular sieves. Then, the filtrate is concentrated under reduced pressure to remove the acetonitrile solvent, and a liquid crude product is obtained.

[0037] (3) purification

[0038] The liquid crude product is subjected to vacuum distillation at a vacuum degree of 50 pa, and 54.3 g of a liquid with a gas chromatographic purity of 99.2% is collected.

[0039] As an optional embodiment of the present application, the additive A-2 is prepared by the following method:

[0040] (1) esterification reaction

[0041] In a 500 mL three-neck flask, 76.7 g (0.5 mol) of phosphorus oxychloride and 153.4 g of 1,2-dichloroethane solvent were added, and stirring was performed while cooling to 15°C. 30.0 g (0.5 mol) of n-propanol was added dropwise over 30 min, and 35.5 g (0.5 mol) of 3-hydroxypropionitrile was further added dropwise. After the addition of the raw material was completed, the temperature was increased to 25°C, and the reaction was further performed for 90 min to obtain a reaction liquid containing a chloro intermediate.

[0042] (2) Fluorination reaction

[0043] In a 1000 mL three-neck flask, the chloro intermediate was added, and 500 mL of acetonitrile solvent was added to perform stirring. 29.0 g (0.5 mol) of potassium fluoride was added in batches while controlling the temperature to 40°C, and the reaction was performed for 3 h to obtain a fluorination reaction liquid. The fluorination reaction liquid was filtered to remove solid salt through a Buchner funnel, and the obtained filtrate was dehydrated to water content <50 ppm through 4A molecular sieves. After that, the filtrate was concentrated under reduced pressure to remove the acetonitrile solvent, and a liquid crude product was obtained.

[0044] (3) Purification

[0045] The liquid crude product was subjected to reduced pressure distillation at a vacuum degree of 50 Pa, and 87.8 g of a liquid with a gas chromatography purity of 99.4% was collected.

[0046] As an optional embodiment of the present application, the additive A-3 is prepared by the following method:

[0047] (1) Esterification reaction

[0048] In a 500 mL three-neck flask, 76.7 g (0.5 mol) of phosphorus oxychloride and 153.4 g of 1,2-dichloroethane solvent were added, and stirring was performed while cooling to 15°C. 23.0 g (0.5 mol) of ethanol was added dropwise over 30 min, and 28.5 g (0.5 mol) of hydroxyacetonitrile was further added dropwise. After the addition of the raw material was completed, the temperature was increased to 25°C, and the reaction was further performed for 90 min to obtain a reaction liquid containing a chloro intermediate. The reaction liquid was transferred to a 500 mL single-neck flask, and concentrated under reduced pressure to remove the 1,2-dichloroethane solvent to obtain the chloro intermediate.

[0049] (2) Fluorination reaction

[0050] In a 1000 mL three-neck flask, the chloro intermediate was added and stirred in 500 mL acetonitrile solvent, and 18.5 g (0.5 mol) of ammonium fluoride was added in batches at 30°C, and the reaction was carried out for 3 h to obtain a fluorination reaction liquid. The fluorination reaction liquid was filtered through a Buchner funnel to remove the solid salt, and the obtained filtrate was dehydrated through 4A molecular sieves to obtain water content <50 ppm, and then the filtrate was concentrated under reduced pressure to remove the acetonitrile solvent to obtain a liquid crude product.

[0051] (3) Purification

[0052] The liquid crude product was subjected to reduced pressure distillation at a vacuum degree of 50 Pa, and 43.4 g of a liquid with a gas chromatographic purity of 99.1% was collected.

[0053] The preparation method of the additive A with other structures is as follows: refer to the above three preparation methods, and adjust the selection of R1 and R2.

[0054] As an optional embodiment of the present application, the additive B comprises at least one of the compounds with the following structure:

[0055] As an optional embodiment of the present application, the additive B with the structure shown in Formula II, The preparation method thereof is as follows:

[0056] esterification reaction was carried out, and the additive B was purified. R3 and R4 were each independently selected from an alkyl group with 1-6 carbon atoms, a fluoroalkyl group with 1-6 carbon atoms, or a cycloalkyl group with 3-6 carbon atoms.

[0057] As an optional embodiment of the present application, the additive B-1 The preparation method thereof is as follows:

[0058] (1) Esterification reaction

[0059] In a 500 mL three-neck flask, 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 and cooled to 0°C; 15.0 g (0.5 mol, 95% content) of 2-chloro-2-oxo-1,3,2-dioxaphospholane was dissolved in 50 g of 1,2-dichloroethane solvent, and the above-mentioned three-neck flask was added dropwise within 2 h. After the addition of the raw material was completed, the temperature was increased to 25°C, and the reaction was continued for 1 h to obtain an esterification reaction liquid. The esterification reaction liquid was filtered through a Buchner funnel to remove triethylamine hydrochloride, and the obtained filtrate was transferred to a 500 mL single-neck flask, and concentrated under reduced pressure to remove the 1,2-dichloroethane solvent to obtain a liquid crude product.

[0060] (2) Purification

[0061] The liquid crude product was subjected to vacuum distillation at a vacuum degree of 10 Pa, and 7.1 g of a liquid with a gas chromatography purity of 99.3% was collected.

[0062] As an optional embodiment of the present application, the additive B-2 is prepared by the following method:

[0063] (1) Esterification reaction

[0064] In a 500 mL three-necked flask, 7.1 g (0.1 mol) of 3-hydroxypropyl cyanide, 10.6 g (0.105 mol) of triethylamine (used as a base) and 100 g of 1,2-dichloroethane solvent were added and cooled to 0°C; 15.7 g (0.5 mol) of 2-chloro-2-oxo-1,3,2-dioxaphospholane was dissolved in 50 g of 1,2-dichloroethane solvent, and the above-mentioned three-necked flask was added dropwise within 2 h. After the addition of the raw material was completed, the temperature was raised to 25°C, and the reaction was continued for 1 h to obtain an esterification reaction liquid. The esterification reaction liquid was filtered through a Buchner funnel to remove triethylamine hydrochloride, and the obtained filtrate was transferred to a 500 mL single-necked flask and concentrated under reduced pressure to remove the 1,2-dichloroethane solvent to obtain a liquid crude product.

[0065] (2) Purification

[0066] The liquid crude product was subjected to vacuum distillation at a vacuum degree of 5 Pa, and 10.5 g of a liquid with a gas chromatography purity of 99.5% was collected.

[0067] The preparation method of the additive B with other structures is described with reference to the above two preparation methods, and the selection of R3 and R4 is adjusted.

[0068] As an optional embodiment of the present application, the tricyano compound includes at least one of the compounds with the following structures:

[0069] In a second aspect, the present application 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 of the first aspect.

[0070] As an optional embodiment of the present application, the electrochemical energy storage unit is a lithium ion battery or a sodium ion battery.

[0071] As an optional embodiment of the present application, the electrochemical energy storage unit is a lithium ion battery.

[0072] The application provides an electrolyte additive combination, which comprises a single-cyan compound and a tri-cyan compound, and the single-cyan compound is selected from additive A and / or additive B. The additive A is a chain phosphonate containing one cyan group, and the additive B is a cyclic phosphonate containing one cyan group. In the design of molecular structure, the additive A and the additive B innovatively combine the cyan group and the phosphonate group, and the additive A or the additive B has good oxidation stability, the cyan group and the phosphonate group are complexed with positive metal ions, the positive electrode can be effectively protected, and the dissolution of the positive metal ions under high temperature and high voltage is reduced. The additive A and the additive B can form phosphorus compound protective films on the negative electrode, inhibit the impedance increase in the battery cycle process, and improve the room temperature cycle performance. The tri-cyan compound has excellent oxidation stability, the cyan group is complexed with the positive metal ions, and the positive electrode can be effectively protected. It is found through experiments that the combination of the single-cyan compound and the tri-cyan compound can play a synergistic effect, can effectively improve the high-temperature storage performance and the high-temperature cycle performance of the battery, and reduce the dissolution amount of cobalt in the negative electrode.

[0073] As an optional embodiment of the application, the mass fraction of the additive A in the electrolyte is 0.2%-3%. If the mass fraction of the additive A is too high (higher than 3%), the kinetic performance is easily deteriorated, for example, the room temperature cycle performance is accelerated to decay, and if the mass fraction of the additive A is too low (lower than 0.2%), the addition is ineffective, so the typical but non-limiting mass fraction of the additive A is 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% and the numerical range between any two points.

[0074] As an optional embodiment of the application, the mass fraction of the additive B in the electrolyte is 0.2%-3%. If the mass fraction of the additive B is too high (higher than 3%), the kinetic performance is easily deteriorated, for example, the room temperature cycle performance is accelerated to decay, and if the mass fraction of the additive B is too low (lower than 0.2%), the addition is ineffective, so the typical but non-limiting mass fraction of the additive B is 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% and the numerical range between any two points.

[0075] As an optional embodiment of the present application, the additive further comprises an additive C, the main role of the additive C is to improve the stability of the electrolyte and the electrode interface, and improve the storage performance and cycle performance of the battery. The additive C comprises at least one of vinylene carbonate, fluoroethylene carbonate, vinyl ethylene carbonate, lithium bisoxalate borate, lithium difluoro oxalate borate, lithium difluorophosphate, lithium tetrafluoroborate, methanediol methylene sulfite, 1,3-propane sulfite, 1,3-propylene sulfite, butene glycol derivative, tris(trimethylsilyl) phosphate, tris(trimethylsilyl) borate, vinyl sulfate, propylene sulfate, vinyl sulfite or tetraethenyl silane.

[0076] As a preferred embodiment of the present application, the additive C comprises fluoroethylene carbonate and 1,3-propane sulfite, and the mass ratio of fluoroethylene carbonate to 1,3-propane sulfite is 10:3.

[0077] As a preferred embodiment of the present application, the additive C comprises fluoroethylene carbonate, 1,3-propane sulfite and lithium difluoro oxalate borate, and the mass ratio of fluoroethylene carbonate, 1,3-propane sulfite and lithium difluoro oxalate borate is 10:3:0.5.

[0078] As a preferred embodiment of the present application, the additive C is fluoroethylene carbonate.

[0079] As a preferred embodiment of the present application, the additive C is 1,3-propane sulfite.

[0080] As a preferred embodiment of the present application, the additive C is methanediol methylene sulfite.

[0081] As an optional embodiment of the present application, the mass fraction of the additive C in the electrolyte is 1% to 15%. The typical but non-limiting mass fraction is 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14% or 15% and any numerical range between any two points.

[0082] As an optional embodiment of the present application, the electrolyte salt comprises at least one of lithium hexafluorophosphate, lithium bisfluorosulfonimide, lithium bis(trifluoromethanesulfonimide), sodium hexafluorophosphate, sodium bisfluorosulfonimide or sodium bis(trifluoromethanesulfonimide).

[0083] As an optional embodiment of the present application, the concentration of the electrolyte salt in the electrolyte is 0.6 mol / L-1.8 mol / L, and the typical but non-limiting concentration is 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 of them.

[0084] As an optional embodiment of the present application, the organic solvent includes at least three of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, propyl propionate, propyl acetate, ethyl propionate, ethyl acetate or 2,2-difluoroethyl acetate.

[0085] As an optional embodiment of the present application, the organic solvent includes ethylene carbonate, propylene carbonate, ethyl propionate and propyl propionate, and the mass ratio of ethylene carbonate, propylene carbonate, ethyl propionate and propyl propionate is 15:15:20:50.

[0086] In a third aspect, the present application provides an electrochemical energy storage unit, comprising the electrolyte additive combination of the first aspect or the electrolyte for electrochemical energy storage unit of the second aspect.

[0087] As an optional embodiment of the present application, the electrochemical energy storage unit is a lithium ion battery or a sodium ion battery.

[0088] As an optional embodiment of the present application, the electrochemical energy storage unit is a lithium ion battery, and the lithium ion battery further comprises a positive electrode, a negative electrode and a separator film between the positive electrode and the negative electrode.

[0089] As an optional embodiment of the present application, the positive electrode active material of the positive electrode includes at least one of nickel-cobalt-manganese ternary material, nickel-cobalt-aluminum ternary material or lithium cobaltate.

[0090] As an optional embodiment of the present application, the negative electrode active material of the negative electrode includes at least one of natural graphite, artificial graphite, silicon, silicon alloy, silicon-carbon or silicon-oxygen.

[0091] In a fourth aspect, the present application provides a power device, comprising the electrolyte additive combination of the first aspect, the electrolyte for electrochemical energy storage unit of the second aspect or the electrochemical energy storage unit of the third aspect.

[0092] As an optional embodiment of the present application, the power device includes at least one of an electric vehicle, an electric ship, an electric aircraft or an electric tool. The electric vehicle includes an electric car, an electric bus, an electric tram, an electric bicycle, an electric motorcycle, an electric scooter, an electric golf cart and an electric truck, etc. The electric vehicle includes a pure electric vehicle or a hybrid electric vehicle, and the hybrid electric vehicle can be a plug-in hybrid electric vehicle. The electric ship includes a ferry, a passenger ship, a tugboat and a sightseeing ship, etc. The electric aircraft includes an electric airplane, an electric helicopter, an electric glider and an electric drone, etc. The electric tool includes an electric drill, an impact drill, an electric hammer, an electric saw, an electric cutter, an electric mower, an electric vacuum cleaner and an electric mixer, etc.

[0093] In the fifth aspect, the present application provides an energy storage device, which includes the electrolyte additive combination of the first aspect, the electrolyte for electrochemical energy storage unit of the second aspect or the electrochemical energy storage unit of the third aspect.

[0094] As an optional embodiment of the present application, the energy storage device is a communication base station or a power grid energy storage, etc.

[0095] Compared with the prior art, the present application has the following beneficial effects:

[0096] The present application provides an electrolyte additive combination, which includes a single-cyano compound and a tri-cyano compound, and the single-cyano compound is selected from an additive A and / or an additive B. The additive A is a chain phosphonate containing one cyano group, and the additive B is a cyclic phosphonate containing one cyano group. In the molecular structure design, the additive A and the additive B innovatively combine the cyano group and the phosphonate group, and the additive A or the additive B both have good oxidation stability, are applied to an electrochemical energy storage unit, and the cyano group and the phosphonate group both have complexation with positive metal ions, so as to effectively protect the positive electrode and reduce the dissolution of the positive metal ions under high temperature and high voltage. The additive A and the additive B can both form a phosphorus compound protective film on the negative electrode, inhibit the impedance increase in the cycle process and improve the room temperature cycle performance. The tri-cyano compound has excellent oxidation stability, is applied to the electrochemical energy storage unit, and the cyano group has complexation with the positive metal ions, so as to effectively protect the positive electrode. It is found through experiments that the combination of the single-cyano compound and the tri-cyano compound can play a synergistic effect and effectively improve the high-temperature storage performance and the high-temperature cycle performance of the battery.

[0097] Other aspects can be apparent after reading and understanding the detailed description. DETAILED DESCRIPTION

[0098] For the purposes of the present application, the technical solutions and advantages thereof, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the embodiments of the present application. Those skilled in the art should understand that the embodiments are only for the purpose of understanding the present application and should not be regarded as a specific limitation on the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application. The process parameters not specified in the following embodiments are generally in accordance with conventional conditions.

[0099] The endpoints of the ranges and any values disclosed in the present application are not limited to the precise values stated. The ranges or values should be construed to be approximations that allow for significant variation. Various ranges of values that end with “'s” or “'a” are inclusive of the endpoints. Any numerical values include increments of one unit, e.g. 1.0 also includes 1.1, 1.2, 1.3, etc. Any numerical value should be considered to be approximate, as though the word “about” preceded the value. Numerous values have been presented herein for purposes of description. The recitation of specific numerical values by themselves is not intended to be limiting. Any numerical value, however, can include increments of one unit, unless the context clearly indicates otherwise. These include increments of one unit in the high or low ten, one unit in the high or low hundred, one unit in the high or low thousand, one unit in the high or low ten-thousand, one unit in the high or low hundred-thousand, and one unit in the high or low million, whether the unit is in the ordinary or metric system of measurement. Moreover, the embodiments are only for the purpose of understanding the present application and should not be regarded as a specific limitation on the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0100] The present application will be described in further detail below in conjunction with specific examples and comparative examples. Those skilled in the art should understand that the embodiments are only for the purpose of understanding the present application and should not be regarded as a specific limitation on the present application. In addition to additives A and additives B prepared according to the above preparation method, other raw materials used in the present application can be obtained from commercially available products. Among them, the specific structures of additives A and additives B in the following examples and comparative examples are shown in Table 1:

[0101] Table 1

[0102] Example 1

[0103] The present embodiment provides a lithium ion battery electrolyte, which comprises an electrolyte additive combination, the electrolyte additive combination comprises an additive A and a tricyano compound; the lithium ion battery electrolyte specifically comprises the following components in mass fraction: electrolyte salt 15%, additive A 2%, tricyano compound 2%, additive C 13%, and the balance is an organic solvent;

[0104] The electrolyte salt is lithium hexafluorophosphate, and the concentration thereof in the electrolyte is 1.2 mol / L;

[0105] The additive A is additive A-1, and the specific structure is shown in Table 1;

[0106] The tricyano compound is 1,3,6-hexanetricarbonitrile (abbreviated as HTCN);

[0107] The additive C comprises fluoroethylene carbonate and 1,3-propane sulfone lactone, and the mass ratio of fluoroethylene carbonate and 1,3-propane sulfone lactone is 10:3;

[0108] The organic solvent includes ethylene carbonate, propylene carbonate, ethyl propionate and propyl propionate, and the mass ratio of ethylene carbonate, propylene carbonate, ethyl propionate and propyl propionate is 15:15:20:50, based on 100% of the total mass of the organic solvent.

[0109] The preparation method of the lithium ion battery electrolyte of the embodiment includes the following steps:

[0110] The ethylene carbonate, propylene carbonate, ethyl propionate and propyl propionate are proportioned to form an organic solvent, then the formula amount of electrolyte salt (lithium hexafluorophosphate) is added to the organic solvent, then the formula amount of additive C (fluorinated ethylene carbonate and 1,3-propane sulfone lactone) is added, then additive A and tricyanide compound are added, and the mixture is uniformly mixed to prepare the lithium ion battery electrolyte.

[0111] Embodiment 2

[0112] The embodiment provides a lithium ion battery electrolyte, wherein except that additive A-1 is replaced by additive A-2, the other raw materials and the amounts are the same as those in embodiment 1.

[0113] The structural formula of additive A-2 is shown in Table 1.

[0114] Embodiment 3

[0115] The embodiment provides a lithium ion battery electrolyte, wherein except that additive A-1 is replaced by additive A-3, the other raw materials and the amounts are the same as those in embodiment 1.

[0116] The structural formula of additive A-3 is shown in Table 1.

[0117] Embodiment 4

[0118] The embodiment provides a lithium ion battery electrolyte, wherein except that the mass fraction of additive A-1 is adjusted from 2% to 0.2%, the other raw materials and the amounts are the same as those in embodiment 1.

[0119] Embodiment 5

[0120] The embodiment provides a lithium ion battery electrolyte, wherein except that the mass fraction of additive A-1 is adjusted from 2% to 1%, the other raw materials and the amounts are the same as those in embodiment 1.

[0121] Embodiment 6

[0122] The embodiment provides a lithium ion battery electrolyte, wherein except that the mass fraction of additive A-1 is adjusted from 2% to 3%, the other raw materials and the amounts are the same as those in embodiment 1.

[0123] Embodiment 7

[0124] This embodiment provides a lithium ion battery electrolyte, in addition to the additive A-1 is replaced by additive B-1, the rest of the raw materials and dosage is same with example 1.

[0125] The structural formula of additive B-1 is shown in table 1.

[0126] Example 8

[0127] This embodiment provides a lithium ion battery electrolyte, in addition to the additive A-1 is replaced by additive B-1, the rest of the raw materials and dosage is same with example 1.

[0128] Example 9

[0129] This embodiment provides a lithium ion battery electrolyte, in addition to the additive A-1 is replaced by additive B-1, the rest of the raw materials and dosage is same with example 1.

[0130] Example 10

[0131] This embodiment provides a lithium ion battery electrolyte, in addition to the additive A-1 is replaced by additive B-2, the rest of the raw materials and dosage is same with example 1.

[0132] The structural formula of additive B-2 is shown in table 1.

[0133] Example 11

[0134] This embodiment provides a lithium ion battery electrolyte, in addition to the additive A-1 is replaced by additive B-1, the rest of the raw materials and dosage is same with example 1.

[0135] Example 12

[0136] This embodiment provides a lithium ion battery electrolyte, in addition to the additive A-1 is replaced by additive B-1, the rest of the raw materials and dosage is same with example 1.

[0137] Example 13

[0138] This embodiment provides a lithium ion battery electrolyte, in addition to the additive A-1 is replaced by additive B-1, the rest of the raw materials and dosage is same with example 1.

[0139] Example 14

[0140] The embodiment provides a lithium ion battery electrolyte, wherein, except that 2% of tricyano compound HTCN is replaced by 3% of 1,3,5-cyclohexanetricarbonitrile in terms of mass fraction, the rest of raw materials and the amount are the same as those in the embodiment 1.

[0141] Embodiment 15

[0142] The embodiment provides a lithium ion battery electrolyte, wherein, except that 2% of tricyano compound HTCN is replaced by 4% of 1,3,5-pentanetricarbonitrile in terms of mass fraction, the rest of raw materials and the amount are the same as those in the embodiment 1.

[0143] Embodiment 16

[0144] The embodiment provides a lithium ion battery electrolyte, wherein, except that the mass fraction of additive C is adjusted to 13.5% from 13%, and the composition of additive C is adjusted to: additive C comprises fluoroethylene carbonate, 1,3-propane sultone and lithium difluoro(oxalato)borate, and the mass ratio of fluoroethylene carbonate, 1,3-propane sultone and lithium difluoro(oxalato)borate is 10:3:0.5; the rest of raw materials and the amount are the same as those in the embodiment 1.

[0145] Embodiment 17

[0146] The embodiment provides a lithium ion battery electrolyte, wherein, except that the mass fraction of additive C is adjusted to 10% from 13%, and the composition of additive C is adjusted to: additive C comprises fluoroethylene carbonate; the rest of raw materials and the amount are the same as those in the embodiment 1.

[0147] Embodiment 18

[0148] The embodiment provides a lithium ion battery electrolyte, wherein, except that the mass fraction of additive C is adjusted to 3% from 13%, and the composition of additive C is adjusted to: additive C comprises 1,3-propane sultone; the rest of raw materials and the amount are the same as those in the embodiment 1.

[0149] Embodiment 19

[0150] The embodiment provides a lithium ion battery electrolyte, wherein, except that the mass fraction of additive C is adjusted to 1% from 13%, and the composition of additive C is adjusted to: additive C comprises methanedisulfonate; the rest of raw materials and the amount are the same as those in the embodiment 1.

[0151] Embodiment 20

[0152] The embodiment provides a lithium ion battery electrolyte, wherein, except that additive C is not contained, the rest of raw materials and the amount are the same as those in the embodiment 1.

[0153] Comparative example 1

[0154] The present comparative example provides a lithium ion battery electrolyte, except that no additive A-1 and tricyano compound HTCN are added, and the rest of the raw materials and the amount are the same as example 1.

[0155] Comparative example 2

[0156] The present comparative example provides a lithium ion battery electrolyte, except that no tricyano compound HTCN is added, and the rest of the raw materials and the amount are the same as example 1.

[0157] Comparative example 3

[0158] The present comparative example provides a lithium ion battery electrolyte, except that no additive A-1 is added, and the rest of the raw materials and the amount are the same as example 1.

[0159] Comparative example 4

[0160] The present comparative example provides a lithium ion battery electrolyte, except that the additive A-1 is replaced by butanedinitrile SN, and the rest of the raw materials and the amount are the same as example 1.

[0161] Comparative example 5

[0162] The present comparative example provides a lithium ion battery electrolyte, except that the mass fraction of 2% of additive A-1 is replaced by 1% of butanedinitrile SN and 2% of adiponitrile ADN, and the rest of the raw materials and the amount are the same as example 1.

[0163] Comparative example 6

[0164] The present comparative example provides a lithium ion battery electrolyte, except that the mass fraction of additive A-1 is adjusted from 2% to 0.05%, and the rest of the raw materials and the amount are the same as example 1.

[0165] Comparative example 7

[0166] The present comparative example provides a lithium ion battery electrolyte, except that the mass fraction of additive A-1 is adjusted from 2% to 3.5%, and the rest of the raw materials and the amount are the same as example 1.

[0167] Comparative example 8

[0168] The present comparative example provides a lithium ion battery electrolyte, except that the mass fraction of tricyano compound HTCN is adjusted from 2% to 4.5%, and the rest of the raw materials and the amount are the same as example 1.

[0169] Application examples 1-20 and comparative application examples 1-8

[0170] The lithium ion battery electrolyte prepared from Examples 1-20 and Comparative Examples 1-8 was made into lithium ion battery application examples 1-20 and comparative application examples 1-8 (i.e., the lithium ion battery electrolyte of Example 1 was made into lithium ion battery application example 1, the lithium ion battery electrolyte of Example 2 was made into lithium ion battery application example 2, the lithium ion battery electrolyte of Comparative Example 1 was made into lithium ion battery comparative application example 1, the lithium ion battery electrolyte of Comparative Example 4 was made into lithium ion battery comparative application example 4, and so on), and the specific preparation method is as follows:

[0171] Preparation of positive electrode sheet: The positive electrode active material lithium cobaltate LB08 (Xiamen Xiatong New Energy Materials Co., Ltd.), conductive agent carbon black (SP), conductive agent carbon nanotube (CNT), and binder polyvinylidene fluoride (PVDF) were fully stirred and mixed in N-methyl pyrrolidone (NMP) solvent at a weight ratio of 97.075:1.0:0.625:1.3 to form a uniform positive electrode slurry. The slurry was coated on the positive electrode current collector aluminum foil, dried, cold-pressed, and the double-sided area density was 355 g / m 2 , the compacted density was 4.0 g / cm 3 , the design gram capacity was 195 mAh / g, and the positive electrode sheet was obtained.

[0172] Preparation of negative electrode sheet: The negative electrode active material artificial graphite QCG-H2 (Shanghai Sunsmart Technology Co., Ltd.), silicon-carbon C ONE-LSC-2 (Zhejiang Lithium-Cen New Material Technology Co., Ltd.), conductive agent carbon black (SP), thickening agent sodium carboxymethyl cellulose (CMC), and binder butadiene rubber were fully stirred and mixed in deionized water solvent at a mass ratio of 91.5:5:0.5:1.4:1.6 to form a uniform negative electrode slurry. The slurry was coated on the negative electrode current collector copper foil, dried, cold-pressed, and the double-sided area density was 160 g / m 2 , the compacted density was 1.6 g / cm 3 , the design gram capacity was 420 mAh / g, and the negative electrode sheet was obtained.

[0173] The positive electrode sheet, PE separator (Shenzhen Xingyuan Material Technology Co., Ltd.), and negative electrode sheet were stacked in order, with the separator in the middle of the positive and negative electrodes to act as a separator. Then the bare cell was obtained by winding. The bare cell was placed in an outer packaging bag, and the electrolyte was injected into the dried battery. After vacuum packaging, standing, formation, shaping, and other processes, a lithium ion battery with a nominal capacity of 1500 mAh was obtained.

[0174] Test conditions

[0175] The lithium ion batteries prepared from application examples 1-20 and comparative application examples 1-8 were tested for electrochemical performance, and the test method was as follows:

[0176] 1. 85°C storage for 8h, 100% SOC (100% SOC is full state of charge)

[0177] (1) Discharge the battery at 0.2C to 3.0V, stand for 10 min;

[0178] (2) Charge at 0.5C CC-CV (constant current-constant voltage) to 4.53V, cut-off current 1 / 20C, stand for 10 min;

[0179] (3) Discharge at 0.5C to 3.0V, stand for 10 min;

[0180] Cycle (2)-(3) twice, record the second discharge capacity Q1;

[0181] (4) Charge at 0.5C CC-CV (constant current-constant voltage) to 4.53V, cut-off current 1 / 20C, measure internal resistance (recorded as R5), voltage (recorded as U1), volume (recorded as V1), thickness (recorded as H1);

[0182] (5) Stand for 8h at 85°C;

[0183] (6) Measure internal resistance (recorded as R6), voltage (recorded as U2), volume (recorded as V2), thickness (recorded as H2) at hot state;

[0184] (7) Stand for 2h at 25°C, measure thickness at normal temperature, recorded as H3;

[0185] (8) Discharge at 0.5C to 3.0V, stand for 10 min, record capacity Q2;

[0186] (9) Charge at 0.5C CC-CV (constant current-constant voltage) to 4.53V, cut-off current 1 / 20C, stand for 10 min;

[0187] (10) Discharge at 0.5C to 3.0V, stand for 10 min;

[0188] (11) Repeat steps (9)-(10) for 2 times, record capacities Q3, Q4;

[0189] Capacity retention rate = Q2 / Q1; Capacity recovery rate = max(Q3:Q4) / Q1, wherein max(Q3:Q4) refers to the maximum value between capacities Q3 and Q4;

[0190] Volume change rate = V2 / V1; Voltage change rate = U2 / U1; Internal resistance change rate = R6 / R5;

[0191] The test data are shown in Table 2.

[0192] 2. Test of cobalt dissolution amount from negative electrode

[0193] Discharge the battery completed above 85℃ high temperature storage test to 3.0V, test as follows:

[0194] (1) Disassemble the battery in the glove box, and cut a certain area of the negative electrode sheet;

[0195] (2) Put the above negative electrode sheet into a PFA digestion tank, weigh and record the sample mass;

[0196] (3) Add 5mL ultrapure water to the PFA digestion tank with the weighed sample, and add 7mL nitric acid. After tightening the lid, put the PFA digestion tank into the graphite digestion furnace and digest at 150℃ for 3h;

[0197] (4) After completing the digestion, take the PFA digestion tank out of the graphite furnace digestion instrument and cool it down. Then filter the cooled digestion solution into a 50mL plastic volumetric flask using a glass funnel with a quantitative filter paper. The inner wall of the PFA digestion tank also needs to be washed into the glass funnel with a quantitative filter paper using ultrapure water, and then diluted to volume with ultrapure water. Shake well and dilute 10 times for testing;

[0198] (5) Dilute the mixed standard containing Ni, Co, Mn and other elements to 0mg / L, 0.05mg / L, 0.10mg / L, 0.20mg / L, 0.50mg / L, 1.00mg / L gradient with 2% volume ratio of nitric acid, and test by ICP-OES;

[0199] (6) Calculate the cobalt content in the sample, i.e. the cobalt dissolution amount of the negative electrode, from the results of the reader test. Take two negative electrode sheets for parallel test each time, and take the average value.

[0200] The test data is shown in Table 2.

[0201] 3. 45℃ cycle test

[0202] (1) 45℃, stand for 2h;

[0203] (2) 0.5C discharge to 3.0V, stand for 10min;

[0204] (3) 0.5C CC-CV (constant current-constant voltage) charge to 4.53V, cutoff current 1 / 20C, stand for 10min;

[0205] (4) 0.7C discharge to 3.0V, stand for 10min;

[0206] (5) Repeat steps (3)-(4) for 300 cycles.

[0207] The 300-week capacity retention rate is calculated using the 300-week capacity and the initial capacity. The test data is shown in Table 3.

[0208] 4. 25 °C cycle test

[0209] (1) 25 °C, stand for 2 h;

[0210] (2) 0.5 C discharge to 3.0 V, stand for 10 min;

[0211] (3) 0.7 C CC-CV (constant current-constant voltage) charge to 4.53 V, cut-off current 1 / 20 C, stand for 10 min;

[0212] (4) 1 C discharge to 3.0 V, stand for 10 min;

[0213] (5) repeat steps (3)-(4) for 500 cycles.

[0214] The 500-week capacity retention rate was calculated using the 500-week capacity and the initial capacity, and the test data are shown in Table 3.

[0215] Table 2

[0216] Table 3

[0217] As can be seen from the data in Tables 2 and 3, the electrochemical performance of the lithium ion batteries (application examples 1-20) prepared using the lithium ion battery electrolyte provided by the embodiments of the present application is significantly higher than the electrochemical performance of the lithium ion batteries (comparative application examples 1-8) prepared using the lithium ion battery electrolyte of the comparative examples.

[0218] Specifically, comparative application examples 1-3 are all comparative experiments of application example 1, mainly to investigate the influence of the addition of monocyano compounds and / or tricyano compounds on the 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 can significantly improve the high-temperature storage performance and high-temperature cycle performance of the battery, and reduce the amount of cobalt dissolved from the negative electrode, in addition, the room temperature cycle performance of the battery is slightly better or comparable, while the single addition of monocyano compounds or tricyano compounds cannot achieve such obvious effect.

[0219] Comparative application examples 4-5 are also comparative experiments of application example 1, mainly to investigate the influence of the combination of dicyano compounds and tricyano compounds on the battery performance. As can be seen from the data in Tables 2-3, the addition of the combination of dicyano compounds and tricyano compounds causes a significant decrease in the performance of the battery in various aspects. It can be seen therefrom that there is a certain synergistic relationship between the monocyano compounds and the tricyano compounds in the present application, and only through the joint action of both, can the high-temperature storage performance and high-temperature cycle performance of the battery be significantly improved, and the amount of cobalt dissolved from the negative electrode be reduced, in addition, the room temperature cycle performance of the battery is slightly better or comparable.

[0220] Comparative Examples 6-8 are also comparative experiments of Example 1, which mainly investigate the influence of the amount of single-cyan compound or triple-cyan compound. As can be seen from the relevant experimental data in Tables 2-3, when the amount of single-cyan compound or triple-cyan compound is too much, the battery performance is affected, and when the amount is too little, the effect cannot be achieved.

[0221] The above only describes preferred embodiments of the present application and is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application is within the protection scope of the claims of the present application.

Claims

1. An electrolyte additive package comprising a monocyano compound selected from the group consisting of Additive A and / or Additive B, the structure of Additive A being shown in Formula I, the structure of Additive B being shown in Formula II, and a tricyano compound, the structure of the tricyano compound being shown in Formula III, R1and R2are each independently selected from an alkyl group having 1-6 carbon atoms, a fluoroalkyl group having 1-6 carbon atoms, or a cycloalkyl group having 3-6 carbon atoms; R3and R4are each independently selected from an alkyl group having 1-6 carbon atoms, a fluoroalkyl group having 1-6 carbon atoms, or a cycloalkyl group having 3-6 carbon atoms.

2. The electrolyte additive package of claim 1, wherein, R1is selected from an alkyl group having 1-4 carbon atoms or a fluoroalkyl group having 1-4 carbon atoms; R2is selected from an alkyl group having 1-4 carbon atoms, a fluoroalkyl group having 1-4 carbon atoms, or a cycloalkyl group having 3-6 carbon atoms; R3is selected from an alkyl group having 1-4 carbon atoms, a fluoroalkyl group having 1-4 carbon atoms, or a cycloalkyl group having 3-6 carbon atoms; R4is selected from an alkyl group having 1-4 carbon atoms or a fluoroalkyl group having 1-4 carbon atoms; R1, R2, R3, and R4are each independently selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, n-pentyl, isopentyl, t-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; The mass ratio of the monocyano compound and the tricyano compound is (0.2-3):(0.2- 4)。 3. The electrolyte additive set according to claim 1 or 2, wherein The additive A comprises at least one of the compounds having the following structure:

4. The electrolyte additive set of claim 1 or 2, wherein, The additive B comprises at least one of the compounds having the following structure:

5. The electrolyte additive set of claim 1 or 2, wherein, The tricyano compound includes at least one of the compounds having the following structure:

6. 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 of any one of claims 1-5. Optionally, the electrochemical energy storage unit is a lithium ion battery or a sodium ion battery. Optionally, the mass fraction of the additive A in the electrolyte is 0.2%-3%. Optionally, the mass fraction of the additive B in the electrolyte is 0.2%-3%.

7. The electrolyte for electrochemical energy storage cells according to claim 6, wherein, The additive further comprises an additive C, wherein the additive C comprises at least one of vinylene carbonate, fluoroethylene carbonate, vinyl ethylene carbonate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium difluorophosphate, lithium tetrafluoroborate, methanediyl dimethanesulfonate, 1,3-propane sultone, 1,3-propene sultone, butene diol derivative, tris(trimethylsilyl) phosphate, tris(trimethylsilyl) borate, ethylene sulfate, propylene sulfate, ethylene sulfite, or tetraethenylsilane. Optionally, the mass fraction of the additive C in the electrolyte is 1%-15%. Optionally, the electrolyte salt comprises 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. Optionally, the concentration of the electrolyte salt in the electrolyte is 0.6 mol / L-1.8 mol / L. Optionally, the organic solvent comprises at least three of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, propyl propionate, propyl acetate, ethyl propionate, ethyl acetate or 2,2-difluoroethyl acetate.

8. An electrochemical energy storage unit comprising the electrolyte additive combination of any one of claims 1-5 or the electrolyte for electrochemical energy storage units of claim 6 or 7; Optionally, the electrochemical energy storage unit is a lithium-ion battery or a sodium-ion battery. Optionally, the electrochemical energy storage unit is a lithium-ion battery, further comprising a positive electrode, a negative electrode, and a separator membrane between the positive electrode and the negative electrode. Optionally, the positive electrode active material of the positive electrode comprises at least one of nickel-cobalt-manganese ternary material, nickel-cobalt-aluminum ternary material or lithium cobaltate. Optionally, the negative electrode active material of the negative electrode comprises at least one of natural graphite, artificial graphite, silicon, silicon alloy, silicon-carbon or silicon-oxygen.

9. A power device comprising the electrolyte additive combination of any one of claims 1-5, the electrolyte for electrochemical energy storage units of any one of claims 6 or 7 or the electrochemical energy storage unit of claim 8; Optionally, the power device comprises at least one of an electric vehicle, an electric ship, an electric aircraft or an electric tool.

10. An energy storage device comprising the electrolyte additive combination of any one of claims 1-5, the electrolyte for electrochemical energy storage units of any one of claims 6 or 7 or the electrochemical energy storage unit of claim 8; Optionally, the energy storage device is a communication base station or a grid energy storage.

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