High-stability lithium ion battery electrolyte and preparation method thereof

Abstract

The invention discloses a high-stability lithium ion battery electrolyte which comprises the following raw materials: LiPF6, ethylene carbonate, dimethyl carbonate and an additive. Compared with the traditional electrolyte, the electrolyte prepared by the method provided by the invention has good stability, and can maintain a high battery capacity retention rate after 100 cycles, thereby improving the use performance and durability of the battery.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion battery electrolyte, and in particular to a high-stability lithium ion battery electrolyte and a preparation method thereof. Background Art

[0002] Commercial lithium-ion electrolytes are mainly composed of LiPF6 conductive salts, linear and cyclic carbonate solvents, and a small amount of functional additives. However, LiPF6 electrolytes have two obvious defects: (1) LiPF6 has poor thermal stability and will decompose at around 105°C; (2) LiPF6 electrolytes have poor thermal stability. When exposed to high temperatures or in the presence of protic impurities, the electrolyte is easily decomposed, destroying the protective film at the interface between the positive and negative electrodes, dissolving the transition metals in the positive electrode material, and causing the carbonate solvent to continue to decompose. Therefore, how to improve the stability of the electrolyte is of great significance to achieving breakthroughs in lithium-ion batteries in terms of high temperature resistance, cycle life, and safety. Summary of the invention

[0003] To this end, the present invention provides a high-stability lithium-ion battery electrolyte, the raw materials of which include LiPF6, ethylene carbonate, dimethyl carbonate and additives, and the preparation method of the electrolyte is:

[0004] (1) Mixing 2-propionic acid amino-4-aminobenzenesulfonic acid, thionyl chloride and diethylamine in a reactor, then sealing the reactor, heating to 120±5° C. and keeping the temperature for more than 60 minutes, magnetically stirring the mixture during the insulation process, cooling naturally to room temperature after the insulation is completed, opening the reactor, and then heating to 80±5° C. in a water bath and keeping the temperature, condensing and reflux during the insulation process, adding chlorosulfonic acid to the reactor under stirring, continuing to stir at a constant temperature of 80±5° C. in a water bath for more than 40 minutes after the addition is completed, collecting the distillation product within the range of 96° C. under a pressure of 600 Pa, and obtaining a primary product;

[0005] (2) mixing the primary product and antimony trifluoride in a flask, stirring the mixture for 2 to 3 hours, filtering to remove excess antimony trifluoride after stirring, then adding dimethyl sulfoxide to the filtered liquid under stirring, stirring for more than 20 minutes after the addition, then adding ferrous oxalate, trimethylsilyl nitrile and tert-butyl hydroperoxide under stirring, heating to 40±3° C. in a water bath after the addition, stirring at a constant temperature for more than 3 hours, collecting a distillation product within a range of 85° C. under a pressure of 130 Pa, adding 1-phenylvinylboronic acid to the distillation product, and obtaining the additive;

[0006] (3) In an argon-protected glove box, the ethylene carbonate and dimethyl carbonate are mixed uniformly to form a solvent, and then the additive is added to the solvent under stirring. After the addition is completed, the mixture is stirred for more than 2 hours to remove water, and then the LiPF6 is added and stirred for more than 30 minutes to obtain the electrolyte.

[0007] Furthermore, in the step (1), the molar ratio of 2-propionic acid amino-4-aminobenzenesulfonic acid, thionyl chloride, diethylamine and chlorosulfonic acid is 2-propionic acid amino-4-aminobenzenesulfonic acid: thionyl chloride: diethylamine: chlorosulfonic acid = 1:3-4:0.6-0.8:1.

[0008] Furthermore, in the step (2), the mass ratio of the primary product to antimony trifluoride is primary product: antimony trifluoride = 10:5-6.

[0009] Furthermore, in the step (2), the amount ratio of dimethyl sulfoxide, ferrous oxalate, trimethyl silane and tert-butyl hydroperoxide added to the filtered liquid is filtered liquid: dimethyl sulfoxide: ferrous oxalate: trimethyl silane: tert-butyl hydroperoxide = 1 mL: 3-4 mL: 0.006-0.008 g: 0.15-0.16 mL: 0.15-0.18 mL.

[0010] Furthermore, in the step (2), the mass ratio of 1-phenylvinylboric acid added to the distillation product is distillation product: 1-phenylvinylboric acid = 10:1-2.

[0011] Furthermore, in the step (3), the ethylene carbonate and dimethyl carbonate are mixed in a volume ratio of ethylene carbonate: dimethyl carbonate = 1:1, the concentration of LiPF6 in the electrolyte is 1 mol / L, and the amount of additive added is such that the mass percentage of the additive in the electrolyte is 1%.

[0012] The beneficial effect of the present invention is that the electrolyte prepared by the method of the present invention has good stability compared with the traditional electrolyte, and can maintain a high battery capacity retention rate after 100 cycles, thereby improving the performance and durability of the battery. The present invention first prepares a primary product containing a sulfonyl group and a chlorine-containing group, and then converts the chlorine-containing group into a fluorine-containing group by substitution with antimony trifluoride. Compared with the carbonyl group in the traditional ethylene carbonate and dimethyl carbonate solvents, the sulfonyl-containing compound introduced by the present invention has a stronger electronegativity, is not easy to lose electrons and be oxidized, and has a higher electrochemical stability and is not easy to fail. At the same time, through fluorination, the additive compounds or the additives and ethylene carbonate and dimethyl carbonate can obtain a stable structure through bridging functional functional groups, and the fluorine atom itself has a high electronegativity and electron-withdrawing ability. After fluorination, the highest occupied molecular orbital energy level of the solvent molecule can be reduced, and the overall electrochemical stability of the solvent can also be improved. Subsequently, ferrous oxalate, trimethylsilane and tert-butyl hydroperoxide were used to introduce cyano groups with strong coordination ability. The cyano groups coordinated with transition metal ions on the positive electrode to reduce the occurrence of side reactions at the interface. At the same time, other components in the solvent were excluded from contacting the positive electrode surface to a certain extent, especially the damage of LiPF6 decomposition products to the positive electrode, thereby inhibiting the dissolution of the positive electrode interface and improving the stability of the battery. By adding 1-phenylvinylboronic acid, the decomposition of the electrolyte can also be inhibited, and a stable SEI film is formed on the surface of the graphite electrode, further improving the stability of the battery. DETAILED DESCRIPTION

[0013] The present invention will be further described below in conjunction with the embodiments.

[0014] Example 1

[0015] A high-stability lithium-ion battery electrolyte, the raw materials of which include LiPF6, ethylene carbonate, dimethyl carbonate and additives, and the preparation method of the electrolyte is as follows:

[0016] (1) Mixing 2-propionic acid amino-4-aminobenzenesulfonic acid, thionyl chloride and diethylamine in a reactor, then closing the reactor, heating to 120° C. and keeping the mixture warm for 60 minutes, magnetically stirring the mixture during the keeping process, cooling naturally to room temperature after the keeping process is completed, opening the reactor, and then heating to 80° C. in a water bath and keeping the mixture warm, condensing and reflux during the keeping process, adding chlorosulfonic acid to the reactor under stirring, wherein the molar ratio of 2-propionic acid amino-4-aminobenzenesulfonic acid, thionyl chloride, diethylamine and chlorosulfonic acid is 2-propionic acid amino-4-aminobenzenesulfonic acid: thionyl chloride: diethylamine: chlorosulfonic acid = 1:3:0.6:1; after the addition is completed, stirring is continued at a constant temperature of 80° C. in a water bath for 40 minutes, and a distillation product within a range of 96° C. under a pressure of 600 Pa is collected to obtain a primary product;

[0017] (2) mixing the primary product and antimony trifluoride in a flask, wherein the mass ratio of the primary product to antimony trifluoride is primary product: antimony trifluoride = 10:5; stirring the mixture for 2 hours, filtering to remove excess antimony trifluoride after the stirring is completed, and then adding dimethyl sulfoxide to the filtered liquid under stirring, stirring for 20 minutes after the addition is completed, and then adding ferrous oxalate, trimethyl silane and tert-butyl hydroperoxide under stirring, and adding dimethyl sulfoxide, ferrous oxalate, trimethyl silane and tert-butyl hydroperoxide to the filtered liquid. The amount ratio of hydrogen is filtered liquid: dimethyl sulfoxide: ferrous oxalate: trimethyl silane: tert-butyl hydroperoxide = 1 mL: 3 mL: 0.006 g: 0.15 mL: 0.15 mL; after the addition is completed, the water bath is heated to 40° C., and then stirred at a constant temperature for 3 hours, and the distillation product at 85° C. under a pressure of 130 Pa is collected, and 1-phenyl vinyl boronic acid is added to the distillation product. The mass ratio of 1-phenyl vinyl boronic acid added to the distillation product is distillation product: 1-phenyl vinyl boronic acid = 10:1; the additive is obtained;

[0018] (3) In an argon-protected glove box, the ethylene carbonate and dimethyl carbonate are mixed uniformly to form a solvent, wherein the ethylene carbonate and dimethyl carbonate are mixed in a volume ratio of ethylene carbonate: dimethyl carbonate = 1:1, and then the additive is added to the solvent under stirring. After the addition is completed, the mixture is stirred for 2 hours to remove water, and then the LiPF6 is added and stirred for 30 minutes to obtain the electrolyte; in the electrolyte, the concentration of LiPF6 is 1 mol / L, and the amount of the additive added is such that the mass percentage of the additive in the electrolyte is 1%.

[0019] Example 2

[0020] A high-stability lithium-ion battery electrolyte, the raw materials of which include LiPF6, ethylene carbonate, dimethyl carbonate and additives, and the preparation method of the electrolyte is as follows:

[0021] (1) Mixing 2-propionic acid amino-4-aminobenzenesulfonic acid, thionyl chloride and diethylamine in a reactor, then closing the reactor, heating to 120° C. and keeping the temperature for 60 minutes, magnetically stirring the mixture during the insulation process, cooling naturally to room temperature after the insulation is completed, opening the reactor, and then heating to 80° C. in a water bath to keep the temperature, condensing and reflux during the insulation process, adding chlorosulfonic acid to the reactor under stirring, wherein the molar ratio of 2-propionic acid amino-4-aminobenzenesulfonic acid, thionyl chloride, diethylamine and chlorosulfonic acid is 2-propionic acid amino-4-aminobenzenesulfonic acid: thionyl chloride: diethylamine: chlorosulfonic acid = 1:3:0.7:1; after the addition is completed, continue to stir at a constant temperature of 80° C. in a water bath for 40 minutes, collect the distillation product within the range of 96° C. under a pressure of 600 Pa, and obtain a primary product;

[0022] (2) mixing the primary product and antimony trifluoride in a flask, wherein the mass ratio of the primary product to antimony trifluoride is primary product: antimony trifluoride = 10:5; stirring the mixture for 2 hours, filtering to remove excess antimony trifluoride after the stirring is completed, and then adding dimethyl sulfoxide to the filtered liquid under stirring, stirring for 20 minutes after the addition is completed, and then adding ferrous oxalate, trimethyl silane and tert-butyl hydroperoxide under stirring, and adding dimethyl sulfoxide, ferrous oxalate, trimethyl silane and tert-butyl hydroperoxide to the filtered liquid. The amount ratio of hydrogen is filtered liquid: dimethyl sulfoxide: ferrous oxalate: trimethyl silane: tert-butyl hydroperoxide = 1 mL: 3 mL: 0.006 g: 0.15 mL: 0.16 mL; after the addition is completed, the water bath is heated to 40° C., and then stirred at a constant temperature for 3 hours, and the distillation product at 85° C. under a pressure of 130 Pa is collected, and 1-phenyl vinyl boronic acid is added to the distillation product. The mass ratio of 1-phenyl vinyl boronic acid added to the distillation product is distillation product: 1-phenyl vinyl boronic acid = 10:1; the additive is obtained;

[0023] (3) In an argon-protected glove box, the ethylene carbonate and dimethyl carbonate are mixed uniformly to form a solvent, wherein the ethylene carbonate and dimethyl carbonate are mixed in a volume ratio of ethylene carbonate: dimethyl carbonate = 1:1, and then the additive is added to the solvent under stirring. After the addition is completed, the mixture is stirred for 2 hours to remove water, and then the LiPF6 is added and stirred for 30 minutes to obtain the electrolyte; in the electrolyte, the concentration of LiPF6 is 1 mol / L, and the amount of the additive added is such that the mass percentage of the additive in the electrolyte is 1%.

[0024] Example 3

[0025] A high-stability lithium-ion battery electrolyte, the raw materials of which include LiPF6, ethylene carbonate, dimethyl carbonate and additives, and the preparation method of the electrolyte is as follows:

[0026] (1) Mixing 2-propionic acid amino-4-aminobenzenesulfonic acid, thionyl chloride and diethylamine in a reactor, then closing the reactor, heating to 120° C. and keeping the temperature for 60 minutes, magnetically stirring the mixture during the insulation process, cooling naturally to room temperature after the insulation is completed, opening the reactor, and then heating to 80° C. in a water bath to keep the temperature, condensing and reflux during the insulation process, adding chlorosulfonic acid to the reactor under stirring, wherein the molar ratio of 2-propionic acid amino-4-aminobenzenesulfonic acid, thionyl chloride, diethylamine and chlorosulfonic acid is 2-propionic acid amino-4-aminobenzenesulfonic acid: thionyl chloride: diethylamine: chlorosulfonic acid = 1:4:0.7:1; after the addition is completed, continue to stir at a constant temperature of 80° C. in a water bath for 40 minutes, collect the distillation product within the range of 96° C. under a pressure of 600 Pa, and obtain a primary product;

[0027] (2) mixing the primary product and antimony trifluoride in a flask, wherein the mass ratio of the primary product to antimony trifluoride is primary product: antimony trifluoride = 10:6; stirring the mixture for 2 hours, filtering to remove excess antimony trifluoride after the stirring is completed, and then adding dimethyl sulfoxide to the filtered liquid under stirring, stirring for 20 minutes after the addition is completed, and then adding ferrous oxalate, trimethyl silane and tert-butyl hydroperoxide under stirring, and adding dimethyl sulfoxide, ferrous oxalate, trimethyl silane and tert-butyl hydroperoxide to the filtered liquid. The amount ratio of hydrogen is filtered liquid: dimethyl sulfoxide: ferrous oxalate: trimethyl silane: tert-butyl hydroperoxide = 1 mL: 4 mL: 0.008 g: 0.16 mL: 0.18 mL; after the addition is completed, the water bath is heated to 40° C., and then stirred at a constant temperature for 3 hours, and the distillation product at 85° C. under a pressure of 130 Pa is collected, and 1-phenyl vinyl boronic acid is added to the distillation product. The mass ratio of 1-phenyl vinyl boronic acid added to the distillation product is distillation product: 1-phenyl vinyl boronic acid = 10:2; the additive is obtained;

[0028] (3) In an argon-protected glove box, the ethylene carbonate and dimethyl carbonate are mixed uniformly to form a solvent, wherein the ethylene carbonate and dimethyl carbonate are mixed in a volume ratio of ethylene carbonate: dimethyl carbonate = 1:1, and then the additive is added to the solvent under stirring. After the addition is completed, the mixture is stirred for 2 hours to remove water, and then the LiPF6 is added and stirred for 30 minutes to obtain the electrolyte; in the electrolyte, the concentration of LiPF6 is 1 mol / L, and the amount of the additive added is such that the mass percentage of the additive in the electrolyte is 1%.

[0029] Example 4

[0030] A high-stability lithium-ion battery electrolyte, the raw materials of which include LiPF6, ethylene carbonate, dimethyl carbonate and additives, and the preparation method of the electrolyte is as follows:

[0031] (1) Mixing 2-propionic acid amino-4-aminobenzenesulfonic acid, thionyl chloride and diethylamine in a reactor, then closing the reactor, heating to 120° C. and keeping the mixture warm for 60 minutes, magnetically stirring the mixture during the insulation process, cooling naturally to room temperature after the insulation is completed, opening the reactor, and then heating to 80° C. in a water bath to keep the mixture warm, condensing and reflux during the insulation process, adding chlorosulfonic acid to the reactor under stirring, wherein the molar ratio of 2-propionic acid amino-4-aminobenzenesulfonic acid, thionyl chloride, diethylamine and chlorosulfonic acid is 2-propionic acid amino-4-aminobenzenesulfonic acid: thionyl chloride: diethylamine: chlorosulfonic acid = 1:4:0.8:1; after the addition is completed, continue to stir at a constant temperature of 80° C. in a water bath for 40 minutes, collect the distillation product within the range of 96° C. under a pressure of 600 Pa, and obtain a primary product;

[0032] (2) mixing the primary product and antimony trifluoride in a flask, wherein the mass ratio of the primary product to antimony trifluoride is primary product: antimony trifluoride = 10:6; stirring the mixture for 2 hours, filtering to remove excess antimony trifluoride after the stirring is completed, and then adding dimethyl sulfoxide to the filtered liquid under stirring, stirring for 20 minutes after the addition is completed, and then adding ferrous oxalate, trimethyl silane and tert-butyl hydroperoxide under stirring, and adding dimethyl sulfoxide, ferrous oxalate, trimethyl silane and tert-butyl hydroperoxide to the filtered liquid. The amount ratio of hydrogen is filtered liquid: dimethyl sulfoxide: ferrous oxalate: trimethyl silane: tert-butyl hydroperoxide = 1 mL: 4 mL: 0.008 g: 0.16 mL: 0.18 mL; after the addition is completed, the water bath is heated to 40° C., and then stirred at a constant temperature for 3 hours, and the distillation product at 85° C. under a pressure of 130 Pa is collected, and 1-phenyl vinyl boronic acid is added to the distillation product. The mass ratio of 1-phenyl vinyl boronic acid added to the distillation product is distillation product: 1-phenyl vinyl boronic acid = 10:2; the additive is obtained;

[0033] (3) In an argon-protected glove box, the ethylene carbonate and dimethyl carbonate are mixed uniformly to form a solvent, wherein the ethylene carbonate and dimethyl carbonate are mixed in a volume ratio of ethylene carbonate: dimethyl carbonate = 1:1, and then the additive is added to the solvent under stirring. After the addition is completed, the mixture is stirred for 2 hours to remove water, and then the LiPF6 is added and stirred for 30 minutes to obtain the electrolyte; in the electrolyte, the concentration of LiPF6 is 1 mol / L, and the amount of the additive added is such that the mass percentage of the additive in the electrolyte is 1%.

[0034] Comparative Example 1

[0035] A comparative lithium-ion battery electrolyte, the raw materials of which include LiPF6, ethylene carbonate and dimethyl carbonate, is prepared by the following method: in an argon-protected glove box, the ethylene carbonate and dimethyl carbonate are uniformly mixed to form a solvent, the ethylene carbonate and dimethyl carbonate are mixed in a volume ratio of ethylene carbonate: dimethyl carbonate = 1:1, stirred for 2 hours, and water is removed, and then the LiPF6 is added and stirred for 30 minutes for homogenization to obtain the electrolyte described in this comparative example; in the electrolyte, the concentration of LiPF6 is 1 mol / L.

[0036] Comparative Example 2

[0037] A comparative lithium-ion battery electrolyte, the raw materials of which include LiPF6, ethylene carbonate, dimethyl carbonate and additives, is prepared by:

[0038] (1) 2-propionic acid amino-4-aminobenzenesulfonic acid, thionyl chloride and diethylamine are mixed in a reactor, and then the reactor is closed and heated to 120° C. for 60 min. During the insulation process, the mixture is magnetically stirred. After the insulation is completed, it is naturally cooled to room temperature, the reactor is opened, and then heated to 80° C. in a water bath for insulation. During the insulation process, condensation and reflux are performed. Chlorosulfonic acid is added to the reactor under stirring, and the molar ratio of 2-propionic acid amino-4-aminobenzenesulfonic acid, thionyl chloride, diethylamine and chlorosulfonic acid used is 2-propionic acid amino-4-aminobenzenesulfonic acid: thionyl chloride: diethylamine: chlorosulfonic acid = 1:4:0.7:1; after the addition is completed, the mixture is stirred at a constant temperature of 80° C. in a water bath for 40 min, and the distillation product at 96° C. under a pressure of 600 Pa is collected to obtain a primary product; as the additive described in this comparative example;

[0039] (2) In an argon-protected glove box, the ethylene carbonate and dimethyl carbonate are mixed uniformly to form a solvent, wherein the ethylene carbonate and dimethyl carbonate are mixed in a volume ratio of ethylene carbonate: dimethyl carbonate = 1:1, and then the additive is added to the solvent under stirring. After the addition is completed, the mixture is stirred for 2 hours to remove water, and then the LiPF6 is added and stirred for 30 minutes to homogenize, thereby obtaining the electrolyte described in this comparative example; in the electrolyte, the concentration of LiPF6 is 1 mol / L, and the amount of the additive added is such that the mass percentage of the additive in the electrolyte is 1%.

[0040] Comparative Example 3

[0041] A comparative lithium-ion battery electrolyte, the raw materials of which include LiPF6, ethylene carbonate, dimethyl carbonate and additives, is prepared by:

[0042] (1) Mixing 2-propionic acid amino-4-aminobenzenesulfonic acid, thionyl chloride and diethylamine in a reactor, then closing the reactor, heating to 120° C. and keeping the temperature for 60 minutes, magnetically stirring the mixture during the insulation process, cooling naturally to room temperature after the insulation is completed, opening the reactor, and then heating to 80° C. in a water bath to keep the temperature, condensing and reflux during the insulation process, adding chlorosulfonic acid to the reactor under stirring, wherein the molar ratio of 2-propionic acid amino-4-aminobenzenesulfonic acid, thionyl chloride, diethylamine and chlorosulfonic acid is 2-propionic acid amino-4-aminobenzenesulfonic acid: thionyl chloride: diethylamine: chlorosulfonic acid = 1:4:0.7:1; after the addition is completed, continue to stir at a constant temperature of 80° C. in a water bath for 40 minutes, collect the distillation product within the range of 96° C. under a pressure of 600 Pa, and obtain a primary product;

[0043] (2) The primary product and antimony trifluoride are mixed in a flask, and the mass ratio of the primary product and antimony trifluoride is primary product: antimony trifluoride = 10:6; the mixture is stirred for 2 hours, and after the stirring is completed, the excess antimony trifluoride is filtered to remove, and then dimethyl sulfoxide is added to the filtered liquid under stirring. After the addition is completed, it is stirred for 20 minutes, and then ferrous oxalate, trimethyl silane and tert-butyl hydroperoxide are added under stirring. The amount ratio of dimethyl sulfoxide, ferrous oxalate, trimethyl silane and tert-butyl hydroperoxide added to the filtered liquid is filtered liquid: dimethyl sulfoxide: ferrous oxalate: trimethyl silane: tert-butyl hydroperoxide = 1mL: 4mL: 0.008g: 0.16mL: 0.18mL; after the addition is completed, it is heated to 40°C in a water bath, and then stirred at a constant temperature for 3 hours, and the distillation product within the range of 85°C under a pressure of 130Pa is collected to obtain the additive described in this comparative example;

[0044] (3) In an argon-protected glove box, the ethylene carbonate and dimethyl carbonate are mixed evenly to form a solvent, wherein the ethylene carbonate and dimethyl carbonate are mixed in a volume ratio of ethylene carbonate: dimethyl carbonate = 1:1, and then the additive is added to the solvent under stirring. After the addition is completed, the mixture is stirred for 2 hours to remove water, and then the LiPF6 is added and stirred for 30 minutes to obtain the electrolyte described in this comparative example; in the electrolyte, the concentration of LiPF6 is 1 mol / L, and the amount of the additive added is such that the mass percentage of the additive in the electrolyte is 1%.

[0045] Example 5

[0046] The graphite pole piece and the lithium sheet were respectively assembled with the electrolyte prepared by the methods described in the above embodiments and comparative examples into CR2016 button batteries. Except for the different electrolytes, the other parts and components of each group of test batteries are exactly the same. A charge and discharge tester was used to perform constant current charge and discharge tests on each group of test batteries. Before the test, the batteries were first charged and discharged for 5 times with a small current of 0.05C for stable activation, and then tested after activation. The test current was 0.2C / 0.2C, the number of cycles was 100 times, and the voltage range was 0.02~2V. The capacity retention rate was obtained, and the capacity retention rate = discharge specific capacity after 100 cycles / first discharge specific capacity × 100%. The results are shown in Table 1.

[0047] As shown in Table 1, the electrolyte prepared by the method of the present invention has good stability compared with the traditional electrolyte, and can maintain a high battery capacity retention rate after 100 cycles, thereby improving the performance and durability of the battery. The present invention first prepares a primary product containing a sulfonyl group and a chlorine-containing group, and then converts the chlorine-containing group into a fluorine-containing group by substitution with antimony trifluoride. Compared with the carbonyl group in the traditional ethylene carbonate and dimethyl carbonate solvents, the sulfonyl-containing compound introduced by the present invention has a stronger electronegativity, is not easy to lose electrons and be oxidized, and also has a higher electrochemical stability and is not easy to fail. At the same time, through fluorination, the additive compounds or the additives and ethylene carbonate and dimethyl carbonate can obtain a stable structure through bridging functional functional groups, and the fluorine atom itself has a very high electronegativity and electron-withdrawing ability. After fluorination, the highest occupied molecular orbital energy level of the solvent molecule can be reduced, and the electrochemical stability of the solvent as a whole can also be improved. Subsequently, ferrous oxalate, trimethylsilane and tert-butyl hydroperoxide were used to introduce cyano groups with strong coordination ability. The cyano groups coordinated with transition metal ions on the positive electrode to reduce the occurrence of side reactions at the interface. At the same time, other components in the solvent were excluded from contacting the positive electrode surface to a certain extent, especially the damage of LiPF6 decomposition products to the positive electrode, thereby inhibiting the dissolution of the positive electrode interface and improving the stability of the battery. By adding 1-phenylvinylboronic acid, the decomposition of the electrolyte can also be inhibited, and a stable SEI film is formed on the surface of the graphite electrode, further improving the stability of the battery.

[0048] Table 1

[0049] Experimental Group Capacity retention rate Example 1 85.7％ Example 2 86.5％ Example 3 86.8％ Example 4 86.2％ Comparative Example 1 61.9％ Comparative Example 2 68.1％ Comparative Example 3 79.0％

[0050] The technical solution provided by the present invention is introduced in detail above. For those skilled in the art, according to the concept of the embodiments of the present invention, there may be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A high-stability lithium-ion battery electrolyte, characterized in that: The raw materials include LiPF6, ethylene carbonate, dimethyl carbonate and additives, and the preparation method of the electrolyte is: (1) Mixing 2-propionic acid amino-4-aminobenzenesulfonic acid, thionyl chloride and diethylamine in a reactor, then sealing the reactor, heating to 120±5° C. and keeping the temperature for more than 60 minutes, magnetically stirring the mixture during the insulation process, cooling naturally to room temperature after the insulation is completed, opening the reactor, and then heating to 80±5° C. in a water bath and keeping the temperature, condensing and reflux during the insulation process, adding chlorosulfonic acid to the reactor under stirring, continuing to stir at a constant temperature of 80±5° C. in a water bath for more than 40 minutes after the addition is completed, collecting the distillation product within the range of 96° C. under a pressure of 600 Pa, and obtaining a primary product; (2) mixing the primary product and antimony trifluoride in a flask, stirring the mixture for 2 to 3 hours, filtering to remove excess antimony trifluoride after stirring, then adding dimethyl sulfoxide to the filtered liquid under stirring, stirring for more than 20 minutes after the addition, then adding ferrous oxalate, trimethylsilyl nitrile and tert-butyl hydroperoxide under stirring, heating to 40±3° C. in a water bath after the addition, stirring at a constant temperature for more than 3 hours, collecting a distillation product within a range of 85° C. under a pressure of 130 Pa, adding 1-phenylvinylboronic acid to the distillation product, and obtaining the additive; (3) In an argon-protected glove box, the ethylene carbonate and dimethyl carbonate are mixed uniformly to form a solvent, and then the additive is added to the solvent under stirring. After the addition is completed, the mixture is stirred for more than 2 hours to remove water, and then the LiPF6 is added and stirred for more than 30 minutes to obtain the electrolyte.

2. A high-stability lithium-ion battery electrolyte according to claim 1, characterized in that: In the step (1), the molar ratio of 2-propionic acid amino-4-aminobenzenesulfonic acid, thionyl chloride, diethylamine and chlorosulfonic acid is 2-propionic acid amino-4-aminobenzenesulfonic acid: thionyl chloride: diethylamine: chlorosulfonic acid = 1:3-4:0.6-0.8:

1.

3. A high-stability lithium-ion battery electrolyte according to claim 1, characterized in that: In the step (2), the mass ratio of the primary product to antimony trifluoride is primary product: antimony trifluoride = 10:5-6.

4. A high-stability lithium-ion battery electrolyte according to claim 1, characterized in that: In the step (2), dimethyl sulfoxide, ferrous oxalate, trimethyl silane and tert-butyl hydroperoxide are added to the filtered liquid in the following ratio: filtered liquid: dimethyl sulfoxide: ferrous oxalate: trimethyl silane: tert-butyl hydroperoxide = 1 mL: 3-4 mL: 0.006-0.008 g: 0.15-0.16 mL: 0.15-0.18 mL.

5. The high-stability lithium-ion battery electrolyte according to claim 1, characterized in that: In the step (2), the mass ratio of 1-phenylvinylboric acid added to the distillation product is distillation product:1-phenylvinylboric acid=10:1-2.

6. A high-stability lithium-ion battery electrolyte according to claim 1, characterized in that: In the step (3), the ethylene carbonate and dimethyl carbonate are mixed in a volume ratio of ethylene carbonate: dimethyl carbonate = 1:1, the concentration of LiPF6 in the electrolyte is 1 mol / L, and the amount of additive added is such that the mass percentage of the additive in the electrolyte is 1%.