An electrolyte for solving the problem of battery core acupuncture and a preparation method thereof

Abstract

The invention relates to the field of batteries, and in particular to an electrolyte for solving the problem of battery core puncture and a preparation method, which are used to solve the problem that the safety performance of the existing battery core puncture is low, resulting in the battery being easy to catch fire and self-ignite. The electrolyte uses solvent, salt and polyfluorinated modified graphene as raw materials, and the solvent is a mixture of multiple components, which can effectively improve the mobility of ions and reduce viscosity while ensuring the dissociation of salt. After adding the enhanced solvent, the wettability of the battery core electrode can be effectively improved, and it has a significant effect on flame retardancy. The salt is a mixture of multiple components, which can improve the compatibility of the electrolyte and the electrode, so that the battery can work stably within a wider voltage range. The addition of polyfluorinated modified graphene can greatly improve the energy density and charge and discharge rate of the battery, and effectively conduct heat, greatly reduce the increase in internal temperature, thereby effectively improving the safety of the battery core puncture.

Description

Technical Field

[0001] The invention relates to the field of batteries, and in particular to an electrolyte for solving the problem of battery core acupuncture and a preparation method thereof. Background Art

[0002] With the deteriorating environment and the harm caused by global warming, the new energy industry has been paid more and more attention. With the rapid development of lithium / sodium ion batteries, new energy vehicles have become a popular trend with many advantages such as environmental protection and low electricity costs. More and more people are buying new energy vehicles. However, the safety performance of new energy vehicles is still a concern. It is not uncommon for new energy vehicle batteries to catch fire, causing serious economic losses or even personal injuries.

[0003] For lithium / sodium ion batteries, when the battery cell is hit or punctured by foreign objects, the short circuit temperature will cause the diaphragm to shrink, which will lead to extremely large contact between the positive and negative areas. The temperature will further rise, reaching the flash point of the electrolyte, and the battery cell will burn. Especially when the battery cell is fully charged, a large amount of active metal elements lithium / sodium will be deposited on the negative electrode. When lithium / sodium metal comes into contact with air, it is easier to catch fire and self-ignite, further increasing the danger of the battery.

[0004] It can be seen that the safety of the battery mainly depends on the electrolyte inside it. Therefore, developing an electrolyte and preparation method to solve the problem of battery cell puncture is of great significance to improving the safety performance of battery cell puncture. Summary of the invention

[0005] In order to overcome the above-mentioned technical problems, the purpose of the present invention is to provide an electrolyte and a preparation method for solving the problem of battery cell puncture, which solves the problem that the safety performance of existing battery cells is low, resulting in the battery being prone to fire and self-ignition, causing serious economic losses or even personal injury.

[0006] The purpose of the present invention can be achieved through the following technical solutions.

[0007] An electrolyte for solving the problem of battery core puncture comprises the following components in parts by weight.

[0008] 70-95 parts of solvent, 5-30 parts of salt, and 1-20 parts of polyfluorinated modified graphene.

[0009] Wherein, the polyfluorinated modified graphene is prepared by the following steps.

[0010] Step a1: Add flake graphite, concentrated sulfuric acid and concentrated nitric acid to a three-necked flask equipped with an agitator and a thermometer, stir and react for 1-2 hours at a temperature of 0-5°C and a stirring rate of 200-300r / min, then add potassium permanganate and continue to stir and react for 1-2 hours, then add deionized water and continue to stir and react for 2-3 hours at a temperature of 45-55°C, then continue to stir and react for 3-5 hours at a temperature of 95-100°C, after the reaction is completed, cool the reaction product to room temperature, then pour it into a hydrogen peroxide solution, then centrifuge, wash the precipitate with hydrochloric acid solution and distilled water for 3-5 times in turn, then place it in a vacuum drying oven, and dry it at a temperature of 70-75°C for 2-3 hours to obtain graphene oxide.

[0011] Step a2: Add graphene oxide and deionized water to a three-necked flask equipped with a stirrer and a thermometer, and ultrasonically disperse for 1-2 hours at an ultrasonic frequency of 35-45kHz, then add hydrofluoric acid and stir the reaction at a temperature of 25-30°C and a stirring rate of 200-300r / min for 2-3 hours, then heat the temperature to 150-160°C and continue stirring the reaction for 15-20 hours. After the reaction is completed, cool the reaction product to room temperature, then pour it into distilled water and soak it for 24-30 hours, then centrifuge it, place the precipitate in a vacuum drying oven, and dry it at a temperature of 50-55°C for 2-3 hours to obtain fluorine-containing graphene.

[0012] Step a3: Add fluorine-containing graphene, dichlorothionyl and N,N-dimethylformamide into a three-necked flask equipped with a stirrer, a thermometer and a reflux condenser, stir and react for 20-30 minutes at a temperature of 25-30°C and a stirring rate of 200-300 r / min, then heat to reflux and continue stirring and reacting for 20-30 hours. After the reaction is completed, the reaction product is cooled to room temperature and then centrifuged. The precipitate is washed with tetrahydrofuran for 2-3 times, and then placed in a vacuum drying oven and dried at a temperature of 50-55°C for 3-5 hours to obtain acyl chloride fluorine-containing graphene.

[0013] Step a4: Add acyl chloride fluorine-containing graphene, perfluoro-1-octanol, p-toluenesulfonic acid and N,N-dimethylformamide to a three-necked flask equipped with a stirrer and a thermometer, stir and react for 20-30 minutes at a temperature of 25-30°C and a stirring rate of 200-300r / min, then heat to 85-90°C and continue stirring and reacting for 8-10 hours. After the reaction is completed, the reaction product is cooled to room temperature and then centrifuged. The precipitate is washed with anhydrous ethanol and saturated brine for 2-3 times in turn, and then placed in a vacuum drying oven and dried at a temperature of 50-55°C for 2-3 hours to obtain polyfluorinated modified graphene.

[0014] As a further solution of the present invention: the usage ratio of the flake graphite, concentrated sulfuric acid, concentrated nitric acid, potassium permanganate and deionized water in step a1 is 1g:30-35mL:10-15g:4-6g:40-50mL.

[0015] As a further solution of the present invention: the mass fraction of the concentrated sulfuric acid in step a1 is 98%; the mass fraction of the concentrated nitric acid is 67%; the mass fraction of the hydrogen peroxide solution is 20-25%; and the mass fraction of the hydrochloric acid solution is 8-10%.

[0016] As a further solution of the present invention: the usage ratio of the graphene oxide, deionized water and hydrofluoric acid in step a2 is 2g:30-40mL:25-30mL.

[0017] As a further solution of the present invention: the mass fraction of the hydrofluoric acid in step a2 is 30-35%.

[0018] As a further solution of the present invention: the usage ratio of the fluorine-containing graphene, dichlorothionyl and N,N-dimethylformamide in step a3 is 5g:60-70mL:40-50mL.

[0019] As a further solution of the present invention: the usage ratio of the acyl chloride fluorinated graphene, perfluoro-1-octanol, p-toluenesulfonic acid and N,N-dimethylformamide in step a4 is 2g: 0.5-4.5g: 0.01-0.03g: 50-60mL.

[0020] As a further solution of the present invention: a method for preparing an electrolyte for solving the problem of acupuncture of battery cells comprises the following steps.

[0021] Step 1: Weigh 70-95 parts of solvent, 5-30 parts of salt, and 1-20 parts of polyfluorinated modified graphene according to weight parts and set aside.

[0022] Step 2: Evenly mix the solvent, salt and polyfluorinated modified graphene to obtain an electrolyte for solving the acupuncture problem of the battery cell.

[0023] As a further embodiment of the present invention: the solvent comprises a base solvent and an enhanced solvent, and the mass of the enhanced solvent is 2-50% of the mass of the base solvent.

[0024] As a further embodiment of the present invention: the base solvent is one or a mixture of two or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl acetate, ethyl acetate, methyl propionate and ethyl propionate.

[0025] As a further embodiment of the present invention: the enhancing solvent is one or a mixture of two or more of perfluorohexane, perfluorocyclohexane, perfluoromethylcyclohexane, perfluorotoluene, toluene, perfluoroheptane, perfluoro-2-butyltetrahydrofuran, perfluorotriethylamine, fluorobenzene, xylene, o-xylene, m-xylene, p-xylene, methyl trifluoroethyl carbonate, bis (2,2,2-trifluoroethyl) carbonate, and perfluorohexane.

[0026] As a further embodiment of the present invention, the salt is one or a mixture of two or more of lithium hexafluorophosphate, sodium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, sodium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, and sodium bis(trifluoromethylsulfonyl)imide.

[0027] Beneficial effects of the present invention.

[0028] The present invention discloses an electrolyte for solving the problem of acupuncture of battery cells and a preparation method thereof. The electrolyte uses solvent, salt and polyfluorinated modified graphene as raw materials. The solvent is a mixture of multiple components, which can effectively improve the mobility of ions and reduce viscosity while ensuring the dissociation of salt. The addition of an enhanced solvent can also effectively improve the wettability of battery cell pole pieces and has a significant effect on flame retardancy. The salt is a mixture of multiple components, which can improve the compatibility of the electrolyte and the electrode, so that the battery can work stably within a wider voltage range, thereby improving the energy density of the battery. The electrolyte has excellent chemical stability and thermal stability, maintains the chemical stability of the electrolyte, and prolongs the service life of the battery. The addition of polyfluorinated modified graphene can greatly improve the energy density and charge and discharge rate of the battery by virtue of its high conductivity and large specific surface area. The large amount of fluorinated functional groups introduced can effectively promote the formation of a uniform and dense solid electrolyte interface layer, thereby reducing the risk of damage to the solid electrolyte interface layer during the acupuncture process. At the same time, the heat is effectively conducted, and the increase in internal temperature is greatly reduced, thereby effectively avoiding the occurrence of thermal runaway of the battery and improving the acupuncture safety of the battery cell.

[0029] In the process of preparing the electrolyte for solving the acupuncture of the battery core, a polyfluorinated modified graphene is first prepared. First, graphene oxide is prepared using flake graphite as a raw material. Then, the graphene oxide is treated with hydrofluoric acid to introduce fluorine elements into the graphene oxide to obtain fluorine-containing graphene. Then, the fluorine-containing graphene is treated with thionyl chloride to convert the carboxyl groups on the fluorine-containing graphene into acyl chloride groups, thereby improving its reaction activity to obtain acyl chloride fluorine-containing graphene. Finally, the acyl chloride fluorine-containing graphene and perfluoro-1-octanol are reacted to react, and the acyl chloride groups on the acyl chloride fluorine-containing graphene react with the hydroxyl groups on the perfluoro-1-octanol. The polyfluorinated modified graphene is a composite structure of graphene grafted with a large number of organic fluorine groups, has excellent electrical conductivity and thermal conductivity, can improve the electrochemical performance and chemical stability of the battery, and the introduced organic fluorine groups can improve their compatibility after coating, so that they can be evenly dispersed in the electrolyte, significantly improving the performance of the electrolyte, and the chemical stability and thermal stability of the large number of fluorine-containing functional groups introduced are excellent, which can further improve the safety of the battery and effectively avoid the occurrence of thermal runaway of the battery. DETAILED DESCRIPTION

[0030] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] Example 1.

[0032] This embodiment is a method for preparing an electrolyte for solving the problem of battery core puncture, comprising the following steps.

[0033] Step S1: 1 g of flake graphite, 30 mL of concentrated sulfuric acid with a mass fraction of 98%, and 10 g of concentrated nitric acid with a mass fraction of 67% are added to a three-necked flask equipped with a stirrer and a thermometer, and stirred for reaction at a temperature of 0°C and a stirring rate of 200 r / min for 1 hour, then 4 g of potassium permanganate is added and the stirring reaction is continued for 1 hour, then 40 mL of deionized water is added and the temperature is raised to 45°C and the stirring reaction is continued for 2 hours, then the temperature is raised to 95°C and the stirring reaction is continued for 3 hours, and the reaction is completed. The reaction product is cooled to room temperature, and then poured into a hydrogen peroxide solution with a mass fraction of 20%, and then centrifuged. The precipitate is washed 3 times with a hydrochloric acid solution with a mass fraction of 8% and distilled water in turn, and then placed in a vacuum drying oven and dried at a temperature of 70°C for 2 hours to obtain graphene oxide.

[0034] Step S2: Add 2 g of graphene oxide and 30 mL of deionized water to a three-necked flask equipped with a stirrer and a thermometer, and ultrasonically disperse for 1 hour at an ultrasonic frequency of 35 kHz. Then, add 25 mL of hydrofluoric acid with a mass fraction of 30% and stir the reaction at a temperature of 25°C and a stirring rate of 200 r / min for 2 hours. Then, heat the temperature to 150°C and continue stirring the reaction for 15 hours. After the reaction is completed, the reaction product is cooled to room temperature, poured into distilled water and soaked for 24 hours, and then centrifuged. The precipitate is placed in a vacuum drying oven and dried at a temperature of 50°C for 2 hours to obtain fluorine-containing graphene.

[0035] Step S3: Add 5 g of fluorine-containing graphene, 60 mL of dichlorothionyl and 40 mL of N,N-dimethylformamide into a three-necked flask equipped with a stirrer, a thermometer and a reflux condenser, and stir the reaction for 20 min at a temperature of 25 ° C and a stirring rate of 200 r / min, then heat the temperature to reflux and continue stirring the reaction for 20 h. After the reaction is completed, the reaction product is cooled to room temperature and then centrifuged. The precipitate is washed twice with tetrahydrofuran, and then placed in a vacuum drying oven and dried at a temperature of 50 ° C for 3 h to obtain acyl chloride fluorine-containing graphene.

[0036] Step S4: Add 2g of acyl chloride fluorine-containing graphene, 0.5g of perfluoro-1-octanol, 0.01g of p-toluenesulfonic acid and 50mL of N,N-dimethylformamide to a three-necked flask equipped with a stirrer and a thermometer, and stir the reaction at a temperature of 25°C and a stirring rate of 200r / min for 20min, then heat the temperature to 85°C and continue stirring the reaction for 8h. After the reaction, the reaction product is cooled to room temperature and then centrifuged. The precipitate is washed twice with anhydrous ethanol and saturated brine in turn, and then placed in a vacuum drying oven and dried at a temperature of 50°C for 2h to obtain polyfluorinated modified graphene.

[0037] Step S5: weigh 77 parts of solvent, 23 parts of salt, and 1 part of polyfluorinated modified graphene in parts by weight for later use; the solvent includes a base solvent and an enhanced solvent, the mass of the enhanced solvent is 15% of the mass of the base solvent; the base solvent is a mixture of propylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a mass ratio of 2:2:1; the enhanced solvent is perfluorohexane; the salt is a mixture of sodium hexafluorophosphate and sodium bis(fluorosulfonyl)imide in a mass ratio of 1:1.

[0038] Step S6: Evenly mix the solvent, salt and polyfluorinated modified graphene to obtain an electrolyte for solving the acupuncture problem of the battery cell.

[0039] Example 2.

[0040] This embodiment is a method for preparing an electrolyte for solving the problem of battery core puncture, comprising the following steps.

[0041] Step S1: 1 g of flake graphite, 32 mL of concentrated sulfuric acid with a mass fraction of 98%, and 12 g of concentrated nitric acid with a mass fraction of 67% are added to a three-necked flask equipped with a stirrer and a thermometer, and stirred for 1.5 h at a temperature of 3 ° C and a stirring rate of 250 r / min, then 5 g of potassium permanganate is added and the stirring reaction is continued for 1.5 h, then 45 mL of deionized water is added and the temperature is raised to 50 ° C and the stirring reaction is continued for 2.5 h, then the temperature is raised to 98 ° C and the stirring reaction is continued for 4 h, and the reaction is completed. The reaction product is cooled to room temperature, and then poured into a hydrogen peroxide solution with a mass fraction of 22%, and then centrifuged. The precipitate is washed 4 times with a hydrochloric acid solution with a mass fraction of 9% and distilled water in turn, and then placed in a vacuum drying oven and dried at a temperature of 72 ° C for 2.5 h to obtain graphene oxide.

[0042] Step S2: Add 2 g of graphene oxide and 35 mL of deionized water to a three-necked flask equipped with a stirrer and a thermometer, and ultrasonically disperse for 1.5 h at an ultrasonic frequency of 40 kHz, then add 28 mL of hydrofluoric acid with a mass fraction of 32% and stir for 2.5 h at a temperature of 28 ° C and a stirring rate of 250 r / min, then heat to 155 ° C and continue stirring for 18 h. After the reaction is completed, the reaction product is cooled to room temperature, then poured into distilled water and soaked for 27 h, then centrifuged, and the precipitate is placed in a vacuum drying oven and dried at a temperature of 52 ° C for 2.5 h to obtain fluorine-containing graphene.

[0043] Step S3: Add 5 g of fluorine-containing graphene, 65 mL of dichlorothionyl and 45 mL of N,N-dimethylformamide into a three-necked flask equipped with a stirrer, a thermometer and a reflux condenser, and stir the reaction for 25 min at a temperature of 28 ° C and a stirring rate of 250 r / min, then heat the mixture to reflux and continue stirring the reaction for 25 h. After the reaction, cool the reaction product to room temperature, then centrifuge it, wash the precipitate with tetrahydrofuran twice, and then place it in a vacuum drying oven and dry it at a temperature of 52 ° C for 4 h to obtain acyl chloride fluorine-containing graphene.

[0044] Step S4: Add 2g of acyl chloride fluorine-containing graphene, 2.5g of perfluoro-1-octanol, 0.02g of p-toluenesulfonic acid and 55mL of N,N-dimethylformamide to a three-necked flask equipped with a stirrer and a thermometer, and stir the reaction for 25min at a temperature of 28°C and a stirring rate of 250r / min. Then, heat the temperature to 88°C and continue stirring the reaction for 9h. After the reaction, cool the reaction product to room temperature and then centrifuge it. Wash the precipitate twice with anhydrous ethanol and saturated brine in turn, then place it in a vacuum drying oven and dry it at a temperature of 52°C for 2.5h to obtain polyfluorinated modified graphene.

[0045] Step S5: Weigh 77 parts of solvent, 23 parts of salt, and 10.5 parts of polyfluorinated modified graphene in parts by weight for later use; the solvent includes a base solvent and an enhanced solvent, the mass of the enhanced solvent is 15% of the mass of the base solvent; the base solvent is a mixture of propylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a mass ratio of 2:2:1; the enhanced solvent is perfluorohexane; the salt is a mixture of sodium hexafluorophosphate and sodium bis(fluorosulfonyl)imide in a mass ratio of 1:1.

[0046] Step S6: Evenly mix the solvent, salt and polyfluorinated modified graphene to obtain an electrolyte for solving the acupuncture problem of the battery cell.

[0047] Example 3.

[0048] This embodiment is a method for preparing an electrolyte for solving the problem of battery core puncture, comprising the following steps.

[0049] Step S1: 1 g of flake graphite, 35 mL of 98% concentrated sulfuric acid and 15 g of 67% concentrated nitric acid were added to a three-necked flask equipped with a stirrer and a thermometer, and stirred for 2 h at a temperature of 5 ° C and a stirring rate of 300 r / min, then 6 g of potassium permanganate was added and the stirring reaction was continued for 2 h, then 50 mL of deionized water was added and the temperature was raised to 55 ° C and the stirring reaction was continued for 3 h, then the temperature was raised to 100 ° C and the stirring reaction was continued for 5 h, and the reaction product was cooled to room temperature after the reaction was completed, and then poured into a 25% hydrogen peroxide solution, and then centrifuged, and the precipitate was washed 5 times with a 10% hydrochloric acid solution and distilled water in turn, and then placed in a vacuum drying oven and dried at a temperature of 75 ° C for 3 h to obtain graphene oxide.

[0050] Step S2: Add 2 g of graphene oxide and 40 mL of deionized water to a three-necked flask equipped with a stirrer and a thermometer, and ultrasonically disperse for 2 h at an ultrasonic frequency of 45 kHz, then add 30 mL of hydrofluoric acid with a mass fraction of 35% and stir for 3 h at a temperature of 30 ° C and a stirring rate of 300 r / min, then heat to 160 ° C and continue stirring for 20 h. After the reaction is completed, the reaction product is cooled to room temperature, then poured into distilled water and soaked for 30 h, then centrifuged, and the precipitate is placed in a vacuum drying oven and dried at a temperature of 55 ° C for 3 h to obtain fluorine-containing graphene.

[0051] Step S3: Add 5 g of fluorine-containing graphene, 70 mL of dichlorothionyl and 50 mL of N,N-dimethylformamide into a three-necked flask equipped with a stirrer, a thermometer and a reflux condenser, and stir the reaction for 30 min at a temperature of 30°C and a stirring rate of 300 r / min, then heat the temperature to reflux and continue stirring the reaction for 30 h. After the reaction is completed, the reaction product is cooled to room temperature and then centrifuged. The precipitate is washed 3 times with tetrahydrofuran, and then placed in a vacuum drying oven and dried at a temperature of 55°C for 5 h to obtain acyl chloride fluorine-containing graphene.

[0052] Step S4: Add 2g of acyl chloride fluorine-containing graphene, 4.5g of perfluoro-1-octanol, 0.03g of p-toluenesulfonic acid and 60mL of N,N-dimethylformamide to a three-necked flask equipped with a stirrer and a thermometer, and stir the reaction for 30min at a temperature of 30°C and a stirring rate of 300r / min, then heat the temperature to 90°C and continue stirring the reaction for 10h. After the reaction, the reaction product is cooled to room temperature and then centrifuged. The precipitate is washed three times with anhydrous ethanol and saturated brine in turn, and then placed in a vacuum drying oven and dried at a temperature of 55°C for 3h to obtain polyfluorinated modified graphene.

[0053] Step S5: Weigh 77 parts of solvent, 23 parts of salt, and 20 parts of polyfluorinated modified graphene in parts by weight for later use; the solvent includes a base solvent and an enhanced solvent, the mass of the enhanced solvent is 15% of the mass of the base solvent; the base solvent is a mixture of propylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a mass ratio of 2:2:1; the enhanced solvent is perfluorohexane; the salt is a mixture of sodium hexafluorophosphate and sodium bis(fluorosulfonyl)imide in a mass ratio of 1:1.

[0054] Step S6: Evenly mix the solvent, salt and polyfluorinated modified graphene to obtain an electrolyte for solving the acupuncture problem of the battery cell.

[0055] Comparative example 1.

[0056] This comparative example is a method for preparing an electrolyte for solving the problem of battery core puncture, comprising the following steps.

[0057] Step S1: 1 g of flake graphite, 35 mL of 98% concentrated sulfuric acid and 15 g of 67% concentrated nitric acid were added to a three-necked flask equipped with a stirrer and a thermometer, and stirred for 2 h at a temperature of 5 ° C and a stirring rate of 300 r / min, then 6 g of potassium permanganate was added and the stirring reaction was continued for 2 h, then 50 mL of deionized water was added and the temperature was raised to 55 ° C and the stirring reaction was continued for 3 h, then the temperature was raised to 100 ° C and the stirring reaction was continued for 5 h, and the reaction product was cooled to room temperature after the reaction was completed, and then poured into a 25% hydrogen peroxide solution, and then centrifuged, and the precipitate was washed 5 times with a 10% hydrochloric acid solution and distilled water in turn, and then placed in a vacuum drying oven and dried at a temperature of 75 ° C for 3 h to obtain graphene oxide.

[0058] Step S2: weigh 77 parts of solvent, 23 parts of salt, and 20 parts of graphene oxide in parts by weight for later use; the solvent includes a base solvent and an enhanced solvent, the mass of the enhanced solvent is 15% of the mass of the base solvent; the base solvent is a mixture of propylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a mass ratio of 2:2:1; the enhanced solvent is perfluorohexane; the salt is a mixture of sodium hexafluorophosphate and sodium bis(fluorosulfonyl)imide in a mass ratio of 1:1.

[0059] Step S3: Evenly mix the solvent, salt and graphene oxide to obtain an electrolyte for solving the acupuncture problem of the battery cell.

[0060] Comparative example 2.

[0061] This comparative example is a method for preparing an electrolyte for solving the problem of battery core puncture, comprising the following steps.

[0062] Step S1: weigh 77 parts of solvent and 23 parts of salt in parts by weight for later use; the solvent includes a base solvent and an enhanced solvent, the mass of the enhanced solvent is 15% of the mass of the base solvent; the base solvent is a mixture of propylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a mass ratio of 2:2:1; the enhanced solvent is perfluorohexane; the salt is a mixture of sodium hexafluorophosphate and sodium bis(fluorosulfonyl)imide in a mass ratio of 1:1.

[0063] Step S2: Evenly mix the solvent and the salt to obtain an electrolyte for solving the acupuncture problem of the battery cell.

[0064] Comparative example 3.

[0065] This comparative example is a method for preparing an electrolyte for solving the problem of battery core puncture, comprising the following steps.

[0066] Step S1: weigh 77 parts of solvent and 23 parts of salt in parts by weight for later use; the solvent is a mixture of propylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a mass ratio of 2:2:1; the salt is a mixture of sodium hexafluorophosphate and sodium bis(fluorosulfonyl)imide in a mass ratio of 1:1.

[0067] Step S2: Evenly mix the solvent and the salt to obtain an electrolyte for solving the acupuncture problem of the battery cell.

[0068] Comparative example 4.

[0069] This comparative example is a method for preparing an electrolyte for solving the problem of battery core puncture, comprising the following steps.

[0070] Step S1: weigh 77 parts of solvent and 23 parts of salt in parts by weight for later use; the solvent includes a base solvent and an enhanced solvent, the mass of the enhanced solvent is 15% of the mass of the base solvent; the base solvent is a mixture of propylene carbonate and ethyl methyl carbonate in a mass ratio of 1:1; the enhanced solvent is perfluorohexane; the salt is a mixture of sodium hexafluorophosphate and sodium bis(fluorosulfonyl)imide in a mass ratio of 1:1.

[0071] Step S2: Evenly mix the solvent and the salt to obtain an electrolyte for solving the acupuncture problem of the battery cell.

[0072] Comparative Example 5.

[0073] This comparative example is a method for preparing an electrolyte for solving the problem of battery core puncture, comprising the following steps.

[0074] Step S1: weigh 77 parts of solvent and 23 parts of salt in parts by weight for later use; the solvent includes a base solvent and an enhanced solvent, the mass of the enhanced solvent is 15% of the mass of the base solvent; the base solvent is a mixture of ethyl methyl carbonate and dimethyl carbonate in a mass ratio of 2:1; the enhanced solvent is perfluorohexane; the salt is a mixture of sodium hexafluorophosphate and sodium bis(fluorosulfonyl)imide in a mass ratio of 1:1.

[0075] Step S2: Evenly mix the solvent and the salt to obtain an electrolyte for solving the acupuncture problem of the battery cell.

[0076] Comparative Example 6.

[0077] This comparative example is a method for preparing an electrolyte for solving the problem of battery core puncture, comprising the following steps.

[0078] Step S1: weigh 77 parts of solvent and 23 parts of salt in parts by weight for later use; the solvent includes a base solvent and an enhanced solvent, the mass of the enhanced solvent is 15% of the mass of the base solvent; the base solvent is a mixture of propylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a mass ratio of 2:2:1; the enhanced solvent is perfluorohexane; and the salt is sodium hexafluorophosphate.

[0079] Step S2: Evenly mix the solvent and the salt to obtain an electrolyte for solving the acupuncture problem of the battery cell.

[0080] Comparative Example 7.

[0081] This comparative example is a method for preparing an electrolyte for solving the problem of battery core puncture, comprising the following steps.

[0082] Step S1: weigh 77 parts of solvent and 23 parts of salt in parts by weight for later use; the solvent includes a base solvent and an enhanced solvent, the mass of the enhanced solvent is 15% of the mass of the base solvent; the base solvent is a mixture of propylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a mass ratio of 2:2:1; the enhanced solvent is perfluorohexane; and the salt is sodium bis(fluorosulfonyl)imide.

[0083] Step S2: Evenly mix the solvent and the salt to obtain an electrolyte for solving the acupuncture problem of the battery cell.

[0084] Performance testing.

[0085] The positive electrode was prepared using a mixed material of m(LiFePO4):m(carbon black):m(PVDF)=8:1:1.

[0086] The negative electrode sheet is prepared using graphite material.

[0087] The diaphragm was prepared using a glass fiber diaphragm.

[0088] The electrolytes for solving the problem of battery core puncture in Examples 1-3 and Comparative Examples 1-7 were used as electrolytes.

[0089] The positive electrode sheet, negative electrode sheet, separator and electrolyte are assembled into a 26700 battery with a theoretical capacity of 3500mAh in a glove box filled with high-purity argon. The 26700 battery is then charged and discharged once at 0.5C, and then fully charged and left to stand for 2 hours to pass a needle puncture test.

[0090] The test results are shown in the following table.

[0091]

[0092] Referring to the data in the above table, based on the comparison between Examples 1-3 and Comparative Examples 1-7, it can be seen that adding polyfluorinated modified graphene and enhanced solvent can significantly improve the full charge capacity and needle puncture pass rate of the battery, and its safety is greatly improved.

[0093] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0094] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the invention or exceed the scope defined in this application, they shall all fall within the protection scope of the present invention.

Claims

1. An electrolyte for solving the problem of battery core puncture, characterized in that: It comprises the following components in parts by weight: 70-95 parts of solvent, 5-30 parts of salt, 1-20 parts of polyfluorinated modified graphene; Wherein, the polyfluorinated modified graphene is prepared by the following steps: Step a1: adding flake graphite, concentrated sulfuric acid and concentrated nitric acid to a three-necked flask equipped with a stirrer and a thermometer, stirring the reaction at a temperature of 0-5°C and a stirring rate of 200-300r / min for 1-2h, then adding potassium permanganate and continuing to stir the reaction for 1-2h, then adding deionized water and heating to 45-55°C and continuing to stir the reaction for 2-3h, then heating to 95-100°C and continuing to stir the reaction for 3-5h, after the reaction is completed, the reaction product is cooled to room temperature, then poured into a hydrogen peroxide solution, then centrifuged, and the precipitate is washed with hydrochloric acid solution and distilled water for 3-5 times in sequence, then placed in a vacuum drying oven, and dried at a temperature of 70-75°C for 2-3h to obtain graphene oxide; Step a2: adding graphene oxide and deionized water to a three-necked flask equipped with a stirrer and a thermometer, ultrasonically dispersing for 1-2 hours at an ultrasonic frequency of 35-45kHz, then adding hydrofluoric acid and stirring the reaction at a temperature of 25-30°C and a stirring rate of 200-300r / min for 2-3 hours, then heating to 150-160°C and continuing to stir the reaction for 15-20 hours, cooling the reaction product to room temperature after the reaction, then pouring it into distilled water and soaking it for 24-30 hours, then centrifuging it, placing the precipitate in a vacuum drying oven, and drying it at a temperature of 50-55°C for 2-3 hours to obtain fluorine-containing graphene; Step a3: adding fluorine-containing graphene, thionyl chloride and N,N-dimethylformamide into a three-necked flask equipped with a stirrer, a thermometer and a reflux condenser, stirring the reaction for 20-30 minutes at a temperature of 25-30°C and a stirring rate of 200-300 r / min, then heating to reflux and continuing to stir the reaction for 20-30 hours, cooling the reaction product to room temperature after the reaction, and then centrifuging it, washing the precipitate with tetrahydrofuran for 2-3 times, and then placing it in a vacuum drying oven, and drying it at a temperature of 50-55°C for 3-5 hours to obtain acyl chloride fluorine-containing graphene; Step a4: Add acyl chloride fluorine-containing graphene, perfluoro-1-octanol, p-toluenesulfonic acid and N,N-dimethylformamide to a three-necked flask equipped with a stirrer and a thermometer, stir and react for 20-30 minutes at a temperature of 25-30°C and a stirring rate of 200-300r / min, then heat to 85-90°C and continue stirring and reacting for 8-10 hours. After the reaction is completed, the reaction product is cooled to room temperature and then centrifuged. The precipitate is washed with anhydrous ethanol and saturated brine for 2-3 times in turn, and then placed in a vacuum drying oven and dried at a temperature of 50-55°C for 2-3 hours to obtain polyfluorinated modified graphene.

2. The electrolyte for solving the problem of battery core puncture according to claim 1, characterized in that: The usage ratio of the flake graphite, concentrated sulfuric acid, concentrated nitric acid, potassium permanganate and deionized water in step a1 is 1g:30-35mL:10-15g:4-6g:40-50mL.

3. The electrolyte for solving the problem of battery core puncture according to claim 1, characterized in that: The mass fraction of the concentrated sulfuric acid in step a1 is 98%; the mass fraction of the concentrated nitric acid is 67%; the mass fraction of the hydrogen peroxide solution is 20-25%; and the mass fraction of the hydrochloric acid solution is 8-10%.

4. The electrolyte for solving the problem of battery core puncture according to claim 1, characterized in that: The usage ratio of the graphene oxide, deionized water and hydrofluoric acid in step a2 is 2g:30-40mL:25-30mL.

5. The electrolyte for solving the problem of battery core puncture according to claim 1, characterized in that: The mass fraction of the hydrofluoric acid in step a2 is 30-35%.

6. The electrolyte for solving the problem of battery core puncture according to claim 1, characterized in that: The usage ratio of the fluorine-containing graphene, thionyl chloride and N,N-dimethylformamide in step a3 is 5g:60-70mL:40-50mL.

7. The electrolyte for solving the problem of battery core puncture according to claim 1, characterized in that: The usage ratio of the acyl chloride fluorinated graphene, perfluoro-1-octanol, p-toluenesulfonic acid and N,N-dimethylformamide in step a4 is 2g: 0.5-4.5g: 0.01-0.03g: 50-60mL.

8. A method for preparing an electrolyte for solving the problem of acupuncture in battery cells according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step 1: Weigh 70-95 parts of solvent, 5-30 parts of salt, and 1-20 parts of polyfluorinated modified graphene according to weight parts, and set aside; Step 2: Evenly mix the solvent, salt and polyfluorinated modified graphene to obtain an electrolyte for solving the acupuncture problem of the battery cell.

9. The method for preparing an electrolyte for solving the problem of acupuncture in battery cells according to claim 8, characterized in that: The solvent includes a base solvent and an enhanced solvent, and the mass of the enhanced solvent is 2-50% of the mass of the base solvent; The base solvent is one or a mixture of two or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl acetate, ethyl acetate, methyl propionate, and ethyl propionate; The enhanced solvent is one of perfluorohexane, perfluorocyclohexane, perfluoromethylcyclohexane, perfluorotoluene, toluene, perfluoroheptane, perfluoro-2-butyltetrahydrofuran, perfluorotriethylamine, fluorobenzene, xylene, o-xylene, m-xylene, p-xylene, methyl trifluoroethyl carbonate, bis (2,2,2-trifluoroethyl) carbonate, and perfluorohexane, or a mixture of two or more thereof.

10. The method for preparing an electrolyte for solving acupuncture problems of battery cells according to claim 8, characterized in that: The salt is one of lithium hexafluorophosphate, sodium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, sodium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, sodium bis(trifluoromethylsulfonyl)imide, or a mixture of two or more thereof.

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