An electrolyte for solving the problem of cell acupuncture and its preparation method

Abstract

The present invention relates to the field of batteries, and specifically relates to an electrolyte for solving the problem of pinprick of battery cells and a preparation method thereof, which is used to solve the problem that the safety of the existing battery cells in terms of pinprick safety performance is low, resulting in easy ignition and spontaneous combustion of the battery; the electrolyte uses a solvent, a salt, and polyfluorinated modified graphene as raw materials. The solvent is a mixture of multiple components, which can effectively improve the ion mobility while ensuring the dissociation of the salt, and can also reduce the viscosity. After adding the enhanced solvent, it can effectively improve the wettability of the battery cell electrode sheet and has a significant effect on flame retardancy. The salt is a mixture of multiple components, which can improve the compatibility between the electrolyte and the electrode, enabling the battery to work stably within a wider voltage range. The addition of polyfluorinated modified graphene can greatly improve the energy density and charge-discharge rate of the battery, and effectively conduct heat, significantly reducing the increase in internal temperature, thereby effectively improving the pinprick safety of the battery cell.

Description

Technical Field

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

[0002] With the increasingly deteriorating environment and the harm caused by global warming, etc., 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 current trend with many advantages such as environmental protection and low electricity costs, and more and more people buy new energy vehicles. However, the safety performance of new energy vehicles is still highly concerned. The problems of battery fires in new energy vehicles, causing serious economic losses and even personal injuries, are not uncommon.

[0003] For lithium / sodium ion batteries, when the core encounters external impact or puncture, it will cause the diaphragm to contract due to short-circuit heating, and then cause the positive and negative electrodes to come into contact with a large area, the temperature will further increase, reaching the flash point of the electrolyte, and the core will burn. Especially when the core is in a fully charged state, a large amount of active metal lithium / sodium is deposited on the negative electrode. When lithium / sodium metal contacts air, it is relatively easy to catch fire and self-ignite, further increasing the danger of the battery.

[0004] It can be seen from this that the safety of the battery mainly depends on its internal electrolyte. Therefore, developing an electrolyte for solving the problem of core acupuncture and a preparation method thereof is of great significance for improving the acupuncture safety performance of the core. Summary of the Invention

[0005] In order to overcome the above technical problems, the purpose of the present invention is to provide an electrolyte for solving the problem of core acupuncture and a preparation method thereof, which solves the problem that the acupuncture safety performance of the existing battery core is low, resulting in the battery being prone to catching fire and self-igniting, causing serious economic losses and even personal injuries.

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

[0007] An electrolyte for solving the problem of core acupuncture, comprising the following components in parts by weight.

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

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

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

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

[0012] Step a3: Add fluorinated graphene, thionyl chloride, 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 min under the conditions of a temperature of 25 - 30°C and a stirring rate of 200 - 300 r / min. Then raise the temperature to reflux and continue to stir and react for 20 - 30 h. After the reaction is completed, cool the reaction product to room temperature, then centrifuge. Wash the precipitate with tetrahydrofuran 2 - 3 times, and then place it in a vacuum drying oven and dry it for 3 - 5 h under the condition of a temperature of 50 - 55°C to obtain acyl chloride fluorinated graphene.

[0013] Step a4: Add acyl chloride fluorinated graphene, perfluoro-1-octanol, p-toluenesulfonic acid, and N,N-dimethylformamide into a three-necked flask equipped with a stirrer and a thermometer. Stir and react for 20 - 30 min under the conditions of a temperature of 25 - 30°C and a stirring rate of 200 - 300 r / min. Then raise the temperature to 85 - 90°C and continue to stir and react for 8 - 10 h. After the reaction is completed, cool the reaction product to room temperature, then centrifuge. Wash the precipitate with absolute ethanol and saturated brine 2 - 3 times successively, and then place it in a vacuum drying oven and dry it for 2 - 3 h under the condition of a temperature of 50 - 55°C to obtain polyfluorinated modified graphene.

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

[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%; the mass fraction of the hydrochloric acid solution is 8 - 10%.

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

[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 dosage ratio of the fluorinated graphene, thionyl chloride and N, N - dimethylformamide in step a3 is 5 g: 60 - 70 mL: 40 - 50 mL.

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

[0020] As a further solution of the present invention: a preparation method of an electrolyte for solving the problem of pinprick of an electric core, comprising the following steps.

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

[0022] Step 2: Mix the solvent, the salt and the polyfluoro - modified graphene evenly to obtain an electrolyte for solving the problem of pinprick of an electric core.

[0023] As a further solution of the present invention: the solvent includes a base solvent and an enhancing solvent, and the mass of the enhancing solvent is 2 - 50% of the mass of the base solvent.

[0024] As a further solution 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, ethyl propionate.

[0025] As a further solution 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, o-xylene, m-xylene, p-xylene, methyltrifluoroethyl carbonate, bis(2,2,2-trifluoroethyl) carbonate.

[0026] As a further solution 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, sodium bis(trifluoromethylsulfonyl)imide.

[0027] Advantages of the present invention.

[0028] An electrolyte for solving the problem of pinprick of an electric core and a preparation method thereof according to the present invention. The electrolyte uses a solvent, a salt, and polyfluorinated modified graphene as raw materials. The solvent is a mixture of multiple components, which can effectively improve the ion mobility while ensuring the dissociation of the salt, and can also reduce the viscosity. After adding the enhancing solvent, the wettability of the electrode sheet of the electric core can be effectively improved, and it has a very significant effect on flame retardancy. The salt is a mixture of multiple components, which can improve the compatibility between the electrolyte and the electrode, enable the battery to work stably within a wider voltage range, thereby improving the energy density of the battery, and has excellent chemical stability and thermal stability, maintaining the chemical stability of the electrolyte and extending the service life of the battery. The addition of polyfluorinated modified graphene can greatly improve the energy density and charge-discharge rate of the battery by virtue of its high conductivity and large specific surface area, and a large number of introduced fluorine-containing functional groups can effectively promote the formation of a uniform and dense solid electrolyte interface layer, reducing the risk of damage to the solid electrolyte interface layer during the pinprick process, and effectively conducting heat, greatly reducing the rise of the internal temperature, thereby effectively avoiding the occurrence of battery thermal runaway and improving the pinprick safety of the electric core.

[0029] In the process of preparing an electrolyte for solving the problem of cell pinprick, a polyfluorinated modified graphene is first prepared. First, graphene oxide is prepared using flake graphite as a raw material. Then, graphene oxide is treated with hydrofluoric acid to introduce fluorine elements into graphene oxide, obtaining fluorinated graphene. After that, the fluorinated graphene is treated with thionyl chloride to convert the carboxyl groups on the fluorinated graphene into acyl chloride groups, enhancing its reactivity, and obtaining acyl chloride-containing fluorinated graphene. Finally, the acyl chloride-containing fluorinated graphene reacts with perfluoro-1-octanol, and the acyl chloride groups on the acyl chloride-containing fluorinated graphene react with the hydroxyl groups on perfluoro-1-octanol, thereby introducing a large amount of fluorine elements to obtain polyfluorinated modified graphene. This polyfluorinated modified graphene is a composite structure with a large number of organic fluorine groups grafted onto graphene, having excellent electrical conductivity and thermal conductivity, capable of enhancing the electrochemical performance and chemical stability of the battery. After being coated with the introduced organic fluorine groups, its compatibility can be improved, enabling it to be evenly dispersed in the electrolyte, significantly enhancing the performance of the electrolyte. Moreover, the introduced large number of fluorine-containing functional groups have excellent chemical stability and thermal stability, which can further improve the safety of the battery and effectively avoid the occurrence of battery thermal runaway. Detailed implementation manners

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. Embodiment 1

[0031] This embodiment is a preparation method of an electrolyte for solving the problem of cell pinprick, including the following steps.

[0032] Step S1: Add 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% into a three-necked flask equipped with a stirrer and a thermometer. Stir and react at a temperature of 0 °C and a stirring rate of 200 r / min for 1 h. Then add 4 g of potassium permanganate and continue to stir and react for 1 h. Then add 40 mL of deionized water and continue to stir and react at a temperature of 45 °C for 2 h. Then raise the temperature to 95 °C and continue to stir and react for 3 h. After the reaction is completed, cool the reaction product to room temperature, then pour it into a hydrogen peroxide solution with a mass fraction of 20%. Then centrifuge, wash the precipitate with a hydrochloric acid solution with a mass fraction of 8% and distilled water three times respectively, and then place it in a vacuum drying oven and dry at a temperature of 70 °C for 2 h to obtain graphene oxide.

[0033] Step S2: Add 2 g of graphene oxide and 30 mL of deionized water into a three-necked flask equipped with a stirrer and a thermometer, ultrasonically disperse for 1 h under the condition of an ultrasonic frequency of 35 kHz, then add 25 mL of hydrofluoric acid with a mass fraction of 30%, and stir and react for 2 h at a temperature of 25°C and a stirring rate of 200 r / min. Then, continue to stir and react for 15 h under the condition of heating to 150°C. After the reaction is completed, cool the reaction product to room temperature, then pour it into distilled water and soak for 24 h, and then centrifuge. Place the precipitate in a vacuum drying oven and dry for 2 h at a temperature of 50°C to obtain fluorinated graphene.

[0034] Step S3: Add 5 g of fluorinated graphene, 60 mL of thionyl chloride, and 40 mL of N,N-dimethylformamide into a three-necked flask equipped with a stirrer, a thermometer, and a reflux condenser, stir and react for 20 min at a temperature of 25°C and a stirring rate of 200 r / min, then continue to stir and react for 20 h under the condition of heating to reflux. After the reaction is completed, cool the reaction product to room temperature, then centrifuge. Wash the precipitate twice with tetrahydrofuran, and then place it in a vacuum drying oven and dry for 3 h at a temperature of 50°C to obtain acyl chloride fluorinated graphene.

[0035] Step S4: Add 2 g of acyl chloride fluorinated graphene, 0.5 g of perfluoro-1-octanol, 0.01 g of p-toluenesulfonic acid, and 50 mL of N,N-dimethylformamide into a three-necked flask equipped with a stirrer and a thermometer, stir and react for 20 min at a temperature of 25°C and a stirring rate of 200 r / min, then continue to stir and react for 8 h under the condition of heating to 85°C. After the reaction is completed, cool the reaction product to room temperature, then centrifuge. Wash the precipitate twice with absolute ethanol and saturated brine respectively, and then place it in a vacuum drying oven and dry for 2 h at a temperature of 50°C to obtain polyfluorinated modified graphene.

[0036] Step S5: Weigh 77 parts of solvent, 23 parts of salt, and 1 part of polyfluorinated modified graphene for standby; the solvent includes a base solvent and an enhancing solvent, and the mass of the enhancing 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 enhancing solvent is perfluorohexane; the salt is a mixture of sodium hexafluorophosphate and sodium bis(fluorosulfonyl)imide in a mass ratio of 1:1.

[0037] Step S6: Mix the solvent, salt, and polyfluorinated modified graphene evenly to obtain an electrolyte for solving the problem of cell pinprick. Example 2

[0038] This example is a preparation method of an electrolyte for solving the problem of cell pinprick, which includes the following steps.

[0039] Step S1: Add 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% into a three-necked flask equipped with a stirrer and a thermometer. Stir and react at a temperature of 3 °C and a stirring rate of 250 r / min for 1.5 h. Then add 5 g of potassium permanganate and continue to stir and react for 1.5 h. Then add 45 mL of deionized water and continue to stir and react at a temperature of 50 °C for 2.5 h. Then continue to stir and react at a temperature of 98 °C for 4 h. After the reaction is completed, cool the reaction product to room temperature, then pour it into a hydrogen peroxide solution with a mass fraction of 22%. Then centrifuge, wash the precipitate successively with a hydrochloric acid solution with a mass fraction of 9% and distilled water 4 times. Then place it in a vacuum drying oven and dry at a temperature of 72 °C for 2.5 h to obtain graphene oxide.

[0040] Step S2: Add 2 g of graphene oxide and 35 mL of deionized water into a three-necked flask equipped with a stirrer and a thermometer. Ultrasonically disperse at an ultrasonic frequency of 40 kHz for 1.5 h. Then add 28 mL of hydrofluoric acid with a mass fraction of 32% and stir and react at a temperature of 28 °C and a stirring rate of 250 r / min for 2.5 h. Then continue to stir and react at a temperature of 155 °C for 18 h. After the reaction is completed, cool the reaction product to room temperature, then pour it into distilled water and soak for 27 h. Then centrifuge, place the precipitate in a vacuum drying oven and dry at a temperature of 52 °C for 2.5 h to obtain fluorinated graphene.

[0041] Step S3: Add 5 g of fluorinated graphene, 65 mL of thionyl chloride, and 45 mL of N,N-dimethylformamide into a three-necked flask equipped with a stirrer, a thermometer, and a reflux condenser. Stir and react at a temperature of 28 °C and a stirring rate of 250 r / min for 25 min. Then continue to stir and react under reflux conditions for 25 h. After the reaction is completed, cool the reaction product to room temperature, then centrifuge, wash the precipitate with tetrahydrofuran 2 times. Then place it in a vacuum drying oven and dry at a temperature of 52 °C for 4 h to obtain acyl chloride fluorinated graphene.

[0042] Step S4: Add 2 g of acyl chloride fluorinated graphene, 2.5 g of perfluoro-1-octanol, 0.02 g of p-toluenesulfonic acid, and 55 mL of N,N-dimethylformamide into a three-necked flask equipped with a stirrer and a thermometer. Stir and react at a temperature of 28 °C and a stirring rate of 250 r / min for 25 min. Then continue to stir and react at a temperature of 88 °C for 9 h. After the reaction is completed, cool the reaction product to room temperature, then centrifuge, wash the precipitate successively with absolute ethanol and saturated brine 2 times. Then place it in a vacuum drying oven and dry at a temperature of 52 °C for 2.5 h to obtain polyfluorinated modified graphene.

[0043] Step S5: Weigh 77 parts by weight of a solvent, 23 parts of a salt, and 10.5 parts of polyfluorinated modified graphene for standby; the solvent includes a base solvent and a reinforcing solvent, and the mass of the reinforcing 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 reinforcing solvent is perfluorohexane; the salt is a mixture of sodium hexafluorophosphate and sodium bis(fluorosulfonyl)imide in a mass ratio of 1:1.

[0044] Step S6: Mix the solvent, the salt, and the polyfluorinated modified graphene evenly to obtain an electrolyte for solving the problem of cell acupuncture. Example 3

[0045] This example is a preparation method of an electrolyte for solving the problem of cell acupuncture, including the following steps.

[0046] Step S1: Add 1 g of flake graphite, 35 mL of concentrated sulfuric acid with a mass fraction of 98%, and 15 g of concentrated nitric acid with a mass fraction of 67% into a three-necked flask equipped with a stirrer and a thermometer. Stir and react at a temperature of 5 °C and a stirring rate of 300 r / min for 2 h. Then add 6 g of potassium permanganate and continue to stir and react for 2 h. Then add 50 mL of deionized water and continue to stir and react at a temperature of 55 °C for 3 h. Then raise the temperature to 100 °C and continue to stir and react for 5 h. After the reaction is completed, cool the reaction product to room temperature, then pour it into a hydrogen peroxide solution with a mass fraction of 25%. Then centrifuge, wash the precipitate with a hydrochloric acid solution with a mass fraction of 10% and distilled water 5 times in sequence, and then place it in a vacuum drying oven and dry it at a temperature of 75 °C for 3 h to obtain graphene oxide.

[0047] Step S2: Add 2 g of graphene oxide and 40 mL of deionized water into a three-necked flask equipped with a stirrer and a thermometer. Ultrasonically disperse it at an ultrasonic frequency of 45 kHz for 2 h. Then add 30 mL of hydrofluoric acid with a mass fraction of 35% and stir and react at a temperature of 30 °C and a stirring rate of 300 r / min for 3 h. Then raise the temperature to 160 °C and continue to stir and react for 20 h. After the reaction is completed, cool the reaction product to room temperature, then pour it into distilled water and soak it for 30 h. Then centrifuge, place the precipitate in a vacuum drying oven and dry it at a temperature of 55 °C for 3 h to obtain fluorinated graphene.

[0048] Step S3: Add 5 g of fluorinated graphene, 70 mL of thionyl chloride, and 50 mL of N,N-dimethylformamide into a three-necked flask equipped with a stirrer, a thermometer, and a reflux condenser. Stir and react for 30 min under the conditions of a temperature of 30 °C and a stirring rate of 300 r / min. Then, raise the temperature to reflux and continue stirring and reacting for 30 h. After the reaction is completed, cool the reaction product to room temperature, then centrifuge. Wash the precipitate with tetrahydrofuran three times, and then place it in a vacuum drying oven and dry it at a temperature of 55 °C for 5 h to obtain acyl chloride fluorinated graphene.

[0049] Step S4: Add 2 g of acyl chloride fluorinated graphene, 4.5 g of perfluoro-1-octanol, 0.03 g of p-toluenesulfonic acid, and 60 mL of N,N-dimethylformamide into a three-necked flask equipped with a stirrer and a thermometer. Stir and react for 30 min under the conditions of a temperature of 30 °C and a stirring rate of 300 r / min. Then, raise the temperature to 90 °C and continue stirring and reacting for 10 h. After the reaction is completed, cool the reaction product to room temperature, then centrifuge. Wash the precipitate with absolute ethanol and saturated brine three times respectively, and then place it in a vacuum drying oven and dry it at a temperature of 55 °C for 3 h to obtain polyfluoro-modified graphene.

[0050] Step S5: Weigh 77 parts of solvent, 23 parts of salt, and 20 parts of polyfluoro-modified graphene by weight for standby; the solvent includes a basic solvent and an enhancing solvent, and the mass of the enhancing solvent is 15% of the mass of the basic solvent; the basic solvent is a mixture of propylene carbonate, ethyl methyl carbonate, and dimethyl carbonate in a mass ratio of 2:2:1; the enhancing solvent is perfluorohexane; the salt is a mixture of sodium hexafluorophosphate and sodium bis(fluorosulfonyl)imide in a mass ratio of 1:1.

[0051] Step S6: Mix the solvent, the salt, and the polyfluoro-modified graphene evenly to obtain an electrolyte for solving the problem of cell acupuncture.

[0052] Comparative Example 1.

[0053] This comparative example is a preparation method of an electrolyte for solving the problem of cell acupuncture, including the following steps.

[0054] Step S1: Add 1 g of flake graphite, 35 mL of concentrated sulfuric acid with a mass fraction of 98%, and 15 g of concentrated nitric acid with a mass fraction of 67% into a three-necked flask equipped with a stirrer and a thermometer. Stir and react for 2 h at a temperature of 5°C and a stirring rate of 300 r / min. Then add 6 g of potassium permanganate and continue to stir and react for 2 h. After that, add 50 mL of deionized water and continue to stir and react for 3 h while heating to 55°C. Then continue to stir and react for 5 h while heating to 100°C. After the reaction is completed, cool the reaction product to room temperature, then pour it into a hydrogen peroxide solution with a mass fraction of 25%. Then centrifuge, wash the precipitate 5 times successively with a hydrochloric acid solution with a mass fraction of 10% and distilled water, and then place it in a vacuum drying oven and dry for 3 h at a temperature of 75°C to obtain graphene oxide.

[0055] Step S2: Weigh 77 parts by weight of solvent, 23 parts by weight of salt, and 20 parts by weight of graphene oxide for later use; the solvent includes a base solvent and an enhancing solvent, and the mass of the enhancing 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 enhancing solvent is perfluorohexane; the salt is a mixture of sodium hexafluorophosphate and sodium bis(fluorosulfonyl)imide in a mass ratio of 1:1.

[0056] Step S3: Mix the solvent, salt, and graphene oxide evenly to obtain an electrolyte for solving the problem of cell needle puncture.

[0057] Comparative Example 2.

[0058] This comparative example is a preparation method of an electrolyte for solving the problem of cell needle puncture, including the following steps.

[0059] Step S1: Weigh 77 parts by weight of solvent and 23 parts by weight of salt for later use; the solvent includes a base solvent and an enhancing solvent, and the mass of the enhancing 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 enhancing solvent is perfluorohexane; the salt is a mixture of sodium hexafluorophosphate and sodium bis(fluorosulfonyl)imide in a mass ratio of 1:1.

[0060] Step S2: Mix the solvent and salt evenly to obtain an electrolyte for solving the problem of cell needle puncture.

[0061] Comparative Example 3.

[0062] This comparative example is a preparation method of an electrolyte for solving the problem of cell needle puncture, including the following steps.

[0063] Step S1: Weigh 77 parts by weight of the solvent and 23 parts by weight of the salt for standby; 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.

[0064] Step S2: Mix the solvent and the salt evenly to obtain the electrolyte for solving the pinprick of the battery cell.

[0065] Comparative Example 4.

[0066] This comparative example is a preparation method of an electrolyte for solving the pinprick of the battery cell, including the following steps.

[0067] Step S1: Weigh 77 parts by weight of the solvent and 23 parts by weight of the salt for standby; the solvent includes a base solvent and an enhancing solvent, and the mass of the enhancing 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 enhancing solvent is perfluorohexane; the salt is a mixture of sodium hexafluorophosphate and sodium bis(fluorosulfonyl)imide in a mass ratio of 1:1.

[0068] Step S2: Mix the solvent and the salt evenly to obtain the electrolyte for solving the pinprick of the battery cell.

[0069] Comparative Example 5.

[0070] This comparative example is a preparation method of an electrolyte for solving the pinprick of the battery cell, including the following steps.

[0071] Step S1: Weigh 77 parts by weight of the solvent and 23 parts by weight of the salt for standby; the solvent includes a base solvent and an enhancing solvent, and the mass of the enhancing 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 enhancing solvent is perfluorohexane; the salt is a mixture of sodium hexafluorophosphate and sodium bis(fluorosulfonyl)imide in a mass ratio of 1:1.

[0072] Step S2: Mix the solvent and the salt evenly to obtain the electrolyte for solving the pinprick of the battery cell.

[0073] Comparative Example 6.

[0074] This comparative example is a preparation method of an electrolyte for solving the pinprick of the battery cell, including the following steps.

[0075] Step S1: Weigh 77 parts by weight of the solvent and 23 parts by weight of the salt for standby; the solvent includes a base solvent and an enhancing solvent, and the mass of the enhancing 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 enhancing solvent is perfluorohexane; the salt is sodium hexafluorophosphate.

[0076] Step S2: Mix the solvent and the salt evenly to obtain the electrolyte for solving the problem of cell pinprick.

[0077] Comparative Example 7.

[0078] This comparative example is a preparation method of an electrolyte for solving the problem of cell pinprick, including the following steps.

[0079] Step S1: Weigh 77 parts by weight of the solvent and 23 parts by weight of the salt for standby; the solvent includes a base solvent and a reinforcing solvent, and the mass of the reinforcing 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 reinforcing solvent is perfluorohexane; the salt is sodium bis(fluorosulfonyl)imide.

[0080] Step S2: Mix the solvent and the salt evenly to obtain the electrolyte for solving the problem of cell pinprick.

[0081] Performance test.

[0082] Use a mixed material of m(LiFePO 4 ): m(carbon black): m(PVDF) = 8:1:1 to prepare the positive electrode sheet.

[0083] Use graphite material to prepare the negative electrode sheet.

[0084] Use a glass fiber separator to prepare the separator.

[0085] Use the electrolytes for solving the problem of cell pinprick in Examples 1-3 and Comparative Examples 1-7 as the electrolytes.

[0086] Assemble the positive electrode sheet, negative electrode sheet, separator, and electrolyte into a 26700 battery in a glove box filled with high-purity argon. Its theoretical capacity is 3500 mAh. Then, perform a 0.5C charge and discharge on the 26700 battery once, and then fully charge the battery and let it stand for 2 h for the pinprick test.

[0087] The test results are shown in the following table.

[0088]

[0089] Referring to the data in the above table, based on the comparison between Examples 1-3 and Comparative Examples 1-7, it can be known that adding polyfluorinated modified graphene and the reinforcing solvent can significantly improve the full charge capacity and pinprick passing rate of the battery, and its safety is greatly improved.

[0090] In the description of this specification, the descriptions referring to terms such as "one embodiment", "example", "specific example", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0091] The above content is only an illustration and explanation of the present invention. Those skilled in the art to which this technology belongs can make various modifications or supplements to the described specific embodiments or use similar ways to replace them, as long as they do not deviate from the invention or exceed the scope defined by this application, they should all belong to 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 or a mixture of two or more of perfluorohexane, perfluorocyclohexane, perfluoromethylcyclohexane, perfluorotoluene, toluene, perfluoroheptane, perfluoro-2-butyltetrahydrofuran, perfluorotriethylamine, fluorobenzene, o-xylene, m-xylene, p-xylene, methyl trifluoroethyl carbonate, and bis(2,2,2-trifluoroethyl) carbonate.

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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