CN107887647A - A kind of 5V high voltages electrolyte for lithium secondary batteries and the lithium secondary battery containing the electrolyte - Google Patents

Abstract

The invention discloses an electrolyte solution for a 5V high-voltage lithium secondary battery, which includes a negative electrode film-forming additive, an electrolyte solution stabilizer, an electrolyte lithium salt and a non-aqueous organic solvent, and is characterized in that the electrolyte solution also includes a positive electrode film-forming Additives and wetting agents; the positive film-forming additives are composed of phenyl anhydrides, and the wetting agents are composed of one or both of glyceryl tristearate and glycerol trioleate; the present invention The purpose is to provide an electrolyte solution for a 5V high-voltage lithium secondary battery. The advantage of the electrolyte is that it can effectively improve the high-temperature storage performance and cycle performance of the 5V high-voltage lithium secondary battery. At the same time, the invention also discloses a 5V high-voltage lithium secondary battery using the electrolytic solution.

Description

A kind of electrolytic solution for 5V high-voltage lithium secondary battery and lithium secondary battery containing the electrolytic solution Battery

technical field

The invention relates to the field of electrolytes for lithium secondary batteries, in particular to an electrolyte for a 5V high-voltage lithium secondary battery, a preparation method thereof, and a lithium secondary battery.

Background technique

Lithium secondary batteries are widely used because of their high energy density and good cycle performance. 5V high-voltage cathode materials have greater development potential and market prospects because of their higher energy density. For example, in the field of electric vehicle batteries, high-voltage cathode materials mean fewer single cells in series, smaller total battery volume, lighter battery quality and higher energy.

However, the existing 5V high-voltage cathode material lithium secondary battery has the following problems: high temperature performance and cycle performance are poor.

At present, there have been some studies on solving the problems of 5V high-voltage lithium secondary batteries from the perspective of electrolyte. For example, the high-voltage electrolyte and lithium secondary battery disclosed in the patent CN201510247185.0 uses a mixture of dinitrile compounds and mononitrile compounds as the electrolyte solvent. For example, patent CN201010291454 discloses a lithium secondary battery electrolyte and a lithium secondary battery containing the electrolyte, which uses a mixture of fluorodinitrile, imidazole compound and fluorosulfoxide as a solvent for the electrolyte. For example, patent CN201310528328 discloses an electrolyte solution for a lithium secondary battery, which uses fluorosilane as a solvent for the electrolyte solution. However, these patents only improve the cycle performance of the battery to a certain extent. Therefore, how to simultaneously improve the high-temperature performance and cycle performance of the high-voltage lithium secondary battery from the perspective of the electrolyte is a problem to be considered by those skilled in the art.

Contents of the invention

Based on this, the object of the present invention is to provide an electrolyte solution for a 5V high-voltage lithium secondary battery to solve the problems of high temperature and poor cycle performance of the 5V high-voltage lithium secondary battery.

The specific technical scheme is as follows: an electrolyte solution for a 5V high-voltage lithium secondary battery, including a negative electrode film-forming additive, an electrolyte stabilizer, an electrolyte lithium salt and a non-aqueous organic solvent, and the electrolyte also includes a positive electrode film-forming additive and wetting agent.

The positive electrode film-forming additive is composed of phenyl anhydrides, which account for 1 to 3% of the total mass of the electrolyte, and the phenyl anhydrides are selected from one or more of the following structural formulas:

Wherein, R ₁ , R ₂ , R ₃ , R ₄ and R ₅ are independently selected from hydrogen or methyl.

The wetting agent is composed of one or two of glyceryl tristearate and triolein, which accounts for 0.1-0.5% of the total mass of the electrolyte.

The negative electrode film-forming additive is composed of one or more of fluoroethylene carbonate, vinylene carbonate, and vinylethylene carbonate, which accounts for 1-15% of the total mass of the electrolyte.

The electrolyte stabilizer is composed of one or two of triphenyl phosphite and dicyclohexylcarbodiimide, which accounts for 0.05-0.1% of the total mass of the electrolyte.

The electrolyte lithium salt is any one of lithium hexafluorophosphate, lithium perchlorate, lithium bisfluorosulfonimide, and lithium hexafluoroarsenate, which accounts for 10-17% of the total mass of the electrolyte.

Described non-aqueous organic solvent is made of ethyl methanesulfonate (EMS), sulfolane (TMS), n-sulfolane (BS), ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate ( DMC), methyl ethyl carbonate (EMC), ethyl acetate (EA), propyl acetate (PA), ethyl propionate (EP), which account for 65-80% of the total mass of the electrolyte %.

Simultaneously, the object of the present invention is also to provide a kind of 5V high-voltage lithium secondary battery, comprise that positive electrode material is a kind of in lithium nickel manganese oxide, cobalt lithium phosphate, lithium manganese phosphate, negative electrode material is lithium titanate, graphite, One of silicon carbon, the electrolyte solution of the lithium secondary battery is any electrolyte solution as described above.

Principle of the present invention and advantage are as follows:

The invention adopts the combination of phenyl anhydride and wetting agent, and the phenyl anhydride additive can form a protective film on the surface of the positive electrode material to protect the positive electrode material from being damaged during high-temperature storage and circulation; the wetting agent can fully wet the electrode sheet with the electrolyte , thereby improving cycle performance. In addition, the electrolytic solution of the present invention is also added with a stabilizer and a negative electrode film-forming agent, and the four types of additives interact to make the performance of the electrolytic solution better. Therefore, the application of the electrolyte can improve the high-temperature storage performance and cycle performance of the lithium secondary battery.

Description of drawings

Fig. 1 is the normal temperature cycle test result figure of embodiment 1 and comparative example 1;

Fig. 2 is the normal temperature cycle test result figure of embodiment 2 and comparative example 2;

Fig. 3 is the normal temperature cycle test result figure of embodiment 3 and comparative example 3;

Fig. 4 is the normal temperature cycle test result figure of embodiment 4 and comparative example 4;

Fig. 5 is the normal temperature cycle test result figure of embodiment 5 and comparative example 5;

Fig. 6 is the normal temperature cycle test result figure of embodiment 6 and comparative example 6;

Fig. 7 is the normal temperature cycle test result figure of embodiment 7 and comparative example 7;

Fig. 8 is the normal temperature cycle test result figure of embodiment 8 and comparative example 8;

Fig. 9 is the normal temperature cycle test result figure of embodiment 9 and comparative example 9;

Fig. 10 is the test result figure of the normal temperature cycle experiment of embodiment 1 and comparative examples 10, 11, 12;

Detailed ways

The present application will be further elaborated below by way of examples.

Example 1

Battery production:

Positive electrode preparation: the positive electrode material ratio is: lithium nickel manganese oxide, acetylene black (conductive agent), polyvinylidene fluoride (PVDF, binder) mass ratio is 95:2.5:2.5. Add PVDF to N-methyl-pyrrolidone, stir evenly at high speed, add acetylene black to the solution, stir evenly, then add lithium nickel manganese oxide and stir evenly to form positive electrode slurry, coat positive electrode slurry on aluminum foil, and The positive electrode sheet is baked, compacted, cut, and welded.

Negative electrode preparation: The ratio of negative electrode materials is silicon-carbon composite material, acetylene black, carboxymethyl cellulose (CMC), and propylene butyl rubber (SBR), with a mass ratio of 95:1.0:1.5:2.5. Add CMC to water, stir at high speed to dissolve completely, then add acetylene black, continue to stir until uniform, continue to add silicon-carbon composite material (Si content is 3%) powder, stir to disperse evenly, add SBR, and disperse into a uniform Negative electrode slurry, coating the negative electrode slurry on the copper foil, baking the negative electrode sheet, compacting, cutting into pieces, and soldering the tabs.

Electrolyte preparation: In a glove box filled with argon (moisture <10ppm, oxygen <1ppm), take a mixture of TMS, EC, DMC, and EMC (mass ratio 1:2:5) accounting for 78.6% of the total mass of the electrolyte :3), add additives fluoroethylene carbonate, vinylene carbonate, vinylethylene carbonate, phthalic anhydride, pyromellitic anhydride, triphenyl phosphite, dicyclohexylcarbonate to the mixed solution successively Diimine, glyceryl tristearate, glycerol trioleate, the added amount accounted for 7.00%, 1.00%, 1.00%, 1.00%, 1.00%, 0.05%, 0.05%, 0.10%, 0.20%, and finally add lithium hexafluorophosphate accounting for 10.00% of the total mass of the electrolyte to the mixed solution, stir evenly to obtain the electrolyte A1 of Example 1.

Preparation of the battery: Wind the obtained positive electrode sheet, negative electrode sheet, and polyethylene separator into a battery cell, put it into a cylindrical battery case, inject the above electrolyte into the battery, and seal it to form a 18650 cylindrical battery. The sample lithium secondary battery S1 of Example 1 was obtained.

Example 2

Adopt the preparation method of embodiment 1 electrolyte to prepare electrolyte A2, the difference is that the additives added are fluoroethylene carbonate, phthalic anhydride, triphenyl phosphite, glyceryl tristearate, and the additions are followed by Accounting for 15.00%, 2.00%, 0.10%, 0.50% of the total mass of the electrolyte, and finally adding lithium hexafluorophosphate accounting for 17.00% of the total mass of the electrolyte to the mixed solution. The remaining components are non-aqueous organic solvents, and the non-aqueous organic solvents are TMS, EC, DMC, and EMC mixed solutions (mass ratio is 1:2:5:3), accounting for 65.40% of the total mass of the electrolyte.

The lithium secondary battery S2 was prepared according to the method of Example 1 by using the above electrolyte solution. The difference is that the positive electrode material is lithium nickel manganese oxide, and the negative electrode material is graphite material; the rest are the same as in embodiment 1.

Example 3

The preparation method of the electrolyte in Example 1 is used to prepare the electrolyte A3, except that the additives added are vinylene carbonate, ethylene carbonate, 3-methyl-benzene-1,2,4,5-tetracarboxylic Acid-1,2,4,5-dianhydride, dicyclohexylcarbodiimide, glycerol trioleate, the added amount accounted for 0.50%, 0.50%, 3.00%, 0.10%, 0.50% of the total mass of the electrolyte in sequence , and finally add lithium hexafluorophosphate accounting for 14.40% of the total mass of the electrolyte to the mixed solution. The remaining components are non-aqueous organic solvents, and the non-aqueous organic solvents are TMS, EC, DMC, and EMC mixed solutions (mass ratio is 1:2:5:3), accounting for 81.0% of the total mass of the electrolyte.

The lithium secondary battery S3 was prepared according to the method of Example 1 by using the above electrolyte solution. The difference is that the positive electrode material is lithium nickel manganese oxide, and the negative electrode material is lithium titanate material; the rest are the same as in embodiment 1.

Example 4

The preparation method of the electrolyte solution in Example 1 is adopted to prepare the electrolyte solution A4. The difference is that the additives added are fluoroethylene carbonate, mellitic anhydride, triphenyl phosphite, and glycerol trioleate. 10.00%, 1.00%, 0.08%, 0.30% of the total mass, and finally add lithium perchlorate accounting for 15.00% of the total mass of the electrolyte to the mixed solution. The remaining components are non-aqueous organic solvents, and the non-aqueous organic solvents are TMS, EC, DMC, and EMC mixed solutions (mass ratio is 1:2:5:3), accounting for 73.62% of the total mass of the electrolyte.

The lithium secondary battery S4 was prepared according to the method of Example 1 by using the above electrolyte solution. The difference is that the positive electrode material is lithium cobalt phosphate, and the negative electrode material is a silicon-carbon composite material (Si content is 3%); the rest are the same as in Example 1.

Example 5

Adopt the preparation method of embodiment 1 electrolyte to prepare electrolyte A5, the difference is that the additive that adds is fluoroethylene carbonate, ethylene carbonate, phthalic anhydride, triphenyl phosphite, tristearic acid Glycerides are added in an amount of 3.00%, 0.50%, 3.00%, 0.07%, and 0.50% of the total mass of the electrolyte, and finally lithium bisfluorosulfonyl imide is added to the mixed solution, accounting for 13.50% of the total mass of the electrolyte. The remaining components are non-aqueous organic solvents, and the non-aqueous organic solvents are TMS, EC, DMC, and EMC mixed solutions (mass ratio is 1:2:5:3), accounting for 79.43% of the total mass of the electrolyte.

The lithium secondary battery S5 was prepared according to the method of Example 1 by using the above electrolyte solution. The difference is that the positive electrode material is lithium cobalt phosphate, and the negative electrode material is graphite material; the rest are the same as in embodiment 1.

Example 6

Adopt the preparation method of embodiment 1 electrolyte to prepare electrolyte A6, the difference is that the additive that adds is fluoroethylene carbonate, pyromellitic anhydride, dicyclohexylcarbodiimide, glycerol trioleate, add-on Accounting for 12.00%, 2.50%, 0.05%, and 0.50% of the total mass of the electrolyte in turn, and finally adding lithium hexafluoroarsenate accounting for 16.00% of the total mass of the electrolyte to the mixed solution. The remaining components are non-aqueous organic solvents, and the non-aqueous organic solvents are TMS, EC, DMC, and EMC mixed solutions (mass ratio is 1:2:5:3), accounting for 68.95% of the total mass of the electrolyte.

The lithium secondary battery S6 was prepared according to the method of Example 1 by using the above electrolyte solution. The difference is that the positive electrode material is lithium cobalt phosphate, and the negative electrode material is lithium titanate; the rest are the same as in embodiment 1.

Example 7

The preparation method of the electrolyte solution in Example 1 is adopted to prepare the electrolyte solution A7, except that the additives added are fluoroethylene carbonate, vinylene carbonate, pyromellitic anhydride, dicyclohexylcarbodiimide, triglyceride oil acid ester, the added amount accounted for 8.00%, 1.00%, 3.00%, 0.10%, 0.50% of the total mass of the electrolyte in sequence, and finally added lithium bisfluorosulfonyl imide accounting for 14.40% of the total mass of the electrolyte to the mixed solution. The remaining components are non-aqueous organic solvents, which are mixed solutions of EMS, EC, PC, DMC, DEC, and PA (mass ratio is 1:2:1:4:1:1); accounting for the total mass of the electrolyte 73.0%.

The lithium secondary battery S7 was prepared according to the method of Example 1 by using the above electrolyte solution. The difference is that the positive electrode material is lithium manganese phosphate, and the negative electrode material is a silicon-carbon composite material (with a Si content of 3%); the rest are the same as in Example 1.

Example 8

Adopt the preparation method of embodiment 1 electrolyte to prepare electrolyte A8, the difference is the additive fluoroethylene carbonate, vinylene carbonate, mellitic anhydride, triphenyl phosphite, dicyclohexylcarbodiimide added, Glycerin trioleate, the addition amount accounts for 8.00%, 1.00%, 2.00%, 0.05%, 0.05%, 0.10% of the total mass of the electrolyte in turn, and finally adds perchloric acid accounting for 16.00% of the total mass of the electrolyte to the mixed solution lithium. The remaining components are non-aqueous organic solvents, which are mixed solutions of BS, EC, DMC and EA (mass ratio is 1:2:6:1), accounting for 72.8% of the total mass of the electrolyte.

The lithium secondary battery S8 was prepared according to the method of Example 1 by using the above electrolytic solution. The difference is that the positive electrode material is lithium manganese phosphate, and the negative electrode material is graphite material; the rest are the same as in Example 1.

Example 9

The preparation method of the electrolyte solution in Example 1 is adopted to prepare the electrolyte solution A9. The difference is that the additives added are fluoroethylene carbonate, pyromellitic anhydride, triphenyl phosphite, and glyceryl tristearate. Accounting for 12.00%, 3.00%, 0.10%, 0.50% of the total mass of the electrolyte, and finally adding lithium hexafluorophosphate accounting for 10.00% of the total mass of the electrolyte to the mixed solution. The remaining components are non-aqueous organic solvents, and the non-aqueous organic solvents are BS, EC, DMC, EP, EMC solutions (mass ratio is 1:1:5:2:1), accounting for 74.4% of the total mass of the electrolyte.

The lithium secondary battery S9 was prepared according to the method of Example 1 by using the above electrolyte solution. The difference is that the positive electrode material is lithium manganese phosphate, and the negative electrode material is lithium titanate; the rest are the same as in embodiment 1.

Comparative example 1

Electrolyte DA1 was prepared by the electrolyte method in Example 1, except that the additives added were phthalic anhydride, pyromellitic anhydride, triphenyl phosphite, dicyclohexylcarbodiimide, and glycerol tristearate ester, glycerol trioleate, the added amount accounted for 1.00%, 1.00%, 0.05%, 0.05%, 0.10%, 0.20% of the total mass of the electrolyte, and finally added lithium hexafluorophosphate accounting for 10.00% of the total mass of the electrolyte to the mixed solution . The remaining components are non-aqueous organic solvents, and the non-aqueous organic solvents are mixed solutions of TMS, EC, DMC and EMC (mass ratio is 1:2:5:3).

The lithium secondary battery DS1 was prepared according to the method of Example 1 by using the above electrolyte solution.

Comparative example 2

Electrolyte DA2 was prepared by using the electrolyte method in Example 1. The difference was that the additives added were phthalic anhydride, triphenyl phosphite, and glyceryl tristearate, and the additions accounted for 2.00% of the total mass of the electrolyte, 0.10%, 0.50%, and finally add lithium hexafluorophosphate accounting for 17.00% of the total mass of the electrolyte to the mixed solution. The remaining components are non-aqueous organic solvents, and the non-aqueous organic solvents are mixed solutions of TMS, EC, DMC and EMC (mass ratio is 1:2:5:3).

The lithium secondary battery DS2 was prepared according to the method of Example 1 by using the above electrolyte solution. The difference is that the positive electrode material is lithium nickel manganese oxide, and the negative electrode material is graphite material; the rest are the same as in embodiment 1.

Comparative example 3

Electrolyte DA3 was prepared by the electrolyte method in Example 1, the difference being that the additives added were vinylene carbonate, ethylene carbonate, dicyclohexylcarbodiimide, and glycerol trioleate. 0.50%, 0.50%, 0.10%, 0.50% of the total mass, and finally add lithium hexafluorophosphate accounting for 14.40% of the total mass of the electrolyte to the mixed solution. The remaining components are non-aqueous organic solvents, and the non-aqueous organic solvents are mixed solutions of TMS, EC, DMC and EMC (mass ratio is 1:2:5:3).

The lithium secondary battery DS3 was prepared according to the method of Example 1 by using the above electrolyte solution. The difference is that the positive electrode material is lithium nickel manganese oxide, and the negative electrode material is silicon carbon lithium titanate material; the rest are the same as in embodiment 1.

Comparative example 4

Electrolyte DA4 was prepared by using the electrolyte method in Example 1. The difference was that the additives added were fluoroethylene carbonate, triphenyl phosphite, and triolein, and the additions accounted for 10.00%, 0.08% of the total mass of the electrolyte in turn. %, 0.30%, and finally add lithium perchlorate accounting for 15.00% of the total mass of the electrolyte to the mixed solution. The remaining components are non-aqueous organic solvents, and the non-aqueous organic solvents are mixed solutions of TMS, EC, DMC and EMC (mass ratio is 1:2:5:3).

The lithium secondary battery DS4 was prepared according to the method of Example 1 by using the above electrolyte solution. The difference is that the positive electrode material is lithium cobalt phosphate, and the negative electrode material is a silicon-carbon composite material (Si content is 3%); the rest are the same as in Example 1.

Comparative example 5

Electrolyte DA5 is prepared by the electrolyte method of Example 1, the difference is that the additives added are fluoroethylene carbonate, ethylene ethylene carbonate, triphenyl phosphite, glyceryl tristearate, and the additions account for 3.00%, 0.50%, 0.070%, 0.50% of the total mass, and finally add lithium bisfluorosulfonyl imide accounting for 13.50% of the total mass of the electrolyte to the mixed solution. The remaining components are non-aqueous organic solvents, and the non-aqueous organic solvents are mixed solutions of TMS, EC, DMC and EMC (mass ratio is 1:2:5:3).

The lithium secondary battery DS5 was prepared according to the method of Example 1 by using the above electrolyte solution. The difference is that the positive electrode material is lithium cobalt phosphate, and the negative electrode material is graphite material; the rest are the same as in embodiment 1.

Comparative example 6

Electrolyte DA6 was prepared by using the electrolyte method in Example 1, except that the additives added were fluoroethylene carbonate, pyromellitic anhydride, and glycerol trioleate, and the additions accounted for 12.00% and 2.50% of the total mass of the electrolyte in turn. %, 0.50%, and finally add lithium hexafluoroarsenate accounting for 16.00% of the total mass of the electrolyte to the mixed solution. The remaining components are non-aqueous organic solvents, and the non-aqueous organic solvents are mixed solutions of TMS, EC, DMC and EMC (mass ratio is 1:2:5:3).

The lithium secondary battery DS6 was prepared according to the method of Example 1 by using the above electrolyte solution. The difference is that the positive electrode material is lithium cobalt phosphate, and the negative electrode material is lithium titanate; the rest are the same as in embodiment 1.

Comparative example 7

Electrolyte DA7 was prepared by using the electrolyte method in Example 1. The difference was that the additives added were fluoroethylene carbonate, vinylene carbonate, pyromellitic anhydride, and glycerol trioleate, and the additions accounted for the total mass of the electrolyte in turn. 8.00%, 1.00%, 3.00%, 0.50%, and finally add lithium bisfluorosulfonyl imide accounting for 14.40% of the total mass of the electrolyte to the mixed solution. The remaining components are non-aqueous organic solvents, and the non-aqueous organic solvents are EMS, EC, PC, DMC, DEC, and PA mixed solutions (mass ratio is 1:2:1:4:1:1).

The lithium secondary battery DS7 was prepared according to the method of Example 1 by using the above electrolyte solution. The difference is that the positive electrode material is lithium manganese phosphate, and the negative electrode material is a silicon-carbon composite material (with a Si content of 3%); the rest are the same as in Example 1.

Comparative example 8

Electrolyte solution DA8 is prepared by the electrolyte method of Example 1, the difference is that the additives added are fluoroethylene carbonate, vinylene carbonate, mellitic anhydride, triphenyl phosphite, dicyclohexylcarbodiimide, and the addition amount Accounting for 8.00%, 1.00%, 2.00%, 0.05%, 0.05% of the total mass of the electrolyte in turn, and finally adding lithium perchlorate accounting for 16.00% of the total mass of the electrolyte to the mixed solution. The remaining components are non-aqueous organic solvents, and the non-aqueous organic solvents are mixed solutions of BS, EC, DMC and EA (mass ratio is 1:2:6:1).

The lithium secondary battery DS8 was prepared according to the method of Example 1 by using the above electrolyte solution. The difference is that the positive electrode material is lithium manganese phosphate, and the negative electrode material is graphite material; the rest are the same as in Example 1.

Comparative example 9

Electrolyte DA9 was prepared by using the electrolyte method in Example 1. The difference was that the additives added were fluoroethylene carbonate, pyromellitic anhydride, and triphenyl phosphite, and the additions accounted for 12.00% and 3.00% of the total mass of the electrolyte in turn. %, 0.10%, and finally add lithium hexafluorophosphate accounting for 10.00% of the total mass of the electrolyte to the mixed solution. The remaining components are non-aqueous organic solvents, and the non-aqueous organic solvents are BS, EC, DMC, EP, EMC liquids (mass ratio is 1:1:5:2:1).

The lithium secondary battery DS9 was prepared according to the method of Example 1 by using the above electrolyte solution. The difference is that the positive electrode material is lithium manganese phosphate, and the negative electrode material is lithium titanate; the rest are the same as in embodiment 1.

Comparative example 10

Adopt the preparation method of embodiment 1 electrolyte to prepare electrolyte DA10, the difference is that the additive that adds is fluoroethylene carbonate, vinylene carbonate, ethylene carbonate, phthalic anhydride, pyromellitic anhydride , triphenyl phosphate, pyridine, glyceryl tristearate, glycerol trioleate, the added amount accounted for 1.00%, 7.00%, 1.00%, 1.00%, 1.00%, 1.00%, 0.05% of the total mass of the electrolyte in turn , 0.05%, 0.10%, 0.20%, and finally add lithium hexafluorophosphate accounting for 10.00% of the total mass of the electrolyte to the mixed solution. The remaining components are non-aqueous organic solvents, and the proportioning ratio is the same as in Example 1. Among them, triphenyl phosphate and pyridine are used as stabilizers.

The lithium secondary battery DS10 was prepared according to the method of Example 1 by using the above electrolyte solution.

Comparative example 11

Adopt the preparation method of embodiment 1 electrolyte to prepare electrolyte DA11, the difference is that the additive that adds is fluoroethylene carbonate, vinylene carbonate, ethylene carbonate, phthalic anhydride, pyromellitic anhydride , triphenyl phosphite, dicyclohexylcarbodiimide, glycerol triacetate, the added amount accounted for 7.00%, 1.00%, 1.00%, 1.00%, 1.00%, 0.05%, 0.05%, 0.30%, and finally add lithium hexafluorophosphate accounting for 10.00% of the total mass of the electrolyte to the mixed solution. The remaining components are non-aqueous organic solvents, and the proportioning ratio is the same as in Example 1. Among them, glycerol triacetate is used as a wetting agent.

The lithium secondary battery DS11 was prepared according to the method of Example 1 by using the above electrolyte solution.

Comparative example 12

Adopt the preparation method of embodiment 1 electrolyte to prepare electrolyte DA11, the difference is that the additive that adds is fluoroethylene carbonate, vinylene carbonate, ethylene carbonate, phthalic anhydride, pyromellitic anhydride , triphenyl phosphite, dicyclohexylcarbodiimide, and glyceryl tripropionate, the added amount accounts for 7.00%, 1.00%, 1.00%, 1.00%, 1.00%, 0.05%, and 0.05% of the total mass of the electrolyte in turn , 0.30%, and finally add lithium hexafluorophosphate accounting for 10.00% of the total mass of the electrolyte to the mixed solution. The remaining components are non-aqueous organic solvents, and the proportioning ratio is the same as in Example 1. Among them, glyceryl tripropionate is used as a wetting agent.

The lithium secondary battery DS12 was prepared according to the method of Example 1 by using the above electrolyte solution.

test experiment

The following experiments were carried out on the batteries obtained in all Examples 1-9 and all Comparative Examples 1-12:

Normal temperature cycle test: the negative electrode of the comparative example and the embodiment was charged and discharged in the range of 1.5 to 3.5V at room temperature with a charge-discharge rate of 0.5C/0.5C for the lithium titanate battery, and the negative electrode was graphite and silicon carbon batteries At room temperature, the charge-discharge cycle test is performed at a charge-discharge rate of 0.5C/0.5C in the range of 3 to 5V, and the cycle discharge capacity is recorded and divided by the discharge capacity of the first cycle to obtain the capacity retention rate. The recorded results are shown in Figure 1 -10.

High-temperature storage experiment: first charge and discharge the lithium titanate material battery with the negative pole of the comparative example and the embodiment at room temperature at room temperature at a charge-discharge rate of 0.5C/0.5C at 1.5-3.5V for 3 times, and then charge at 0.5C to 3.5V , Record the third discharge capacity. Store the battery in an oven at 60°C for 7 days, wait for the battery to cool down to room temperature, then charge and discharge 3 times at 1.5-3.5V at a charge-discharge rate of 0.5C/0.5C at room temperature, and record the first discharge capacity and the first discharge capacity. 3 discharge capacity. Divide the first discharge capacity after storage by the third discharge capacity before storage to get the capacity retention rate, divide the third discharge capacity after storage by the third discharge capacity before storage to get the capacity recovery rate, the results are recorded in the table 1.

Charge and discharge the graphite and silicon carbon batteries with negative poles of comparative examples and examples at room temperature at 3-5V for 3 times at a charge-discharge rate of 0.5C/0.5C, then charge to 5V at 0.5C, and record the third discharge capacity. Store the battery in an oven at 60°C for 7 days, wait for the battery to cool down to room temperature, then charge and discharge 3 times at 3-5V at a charge-discharge rate of 0.5C/0.5C at room temperature, and record the first discharge capacity and the third discharge capacity. secondary discharge capacity. Divide the first discharge capacity after storage by the third discharge capacity before storage to get the capacity retention rate, divide the third discharge capacity after storage by the third discharge capacity before storage to get the capacity recovery rate, the results are recorded in the table 1.

Table 1: Test results of capacity retention rate and capacity recovery rate of lithium secondary batteries

Combined with the results of Figure 1, Figure 2 and Table 1, it shows that: S1 is compared with SD1, S2 is compared with SD2, the negative electrode film-forming agent additive is added to the electrolyte, and the battery cycle performance and high-temperature storage performance are significantly improved, indicating that fluoroethylene carbonate, Vinylene carbonate and ethylene carbonate can form a film on the surface of the negative electrode material to improve battery performance.

Combining the results of Figure 3, Figure 4, Figure 5 and Table 1 shows: S3 compared with DS3, S4 compared with SD4, S5 compared with SD5, the positive electrode film-forming additive phenyl anhydride compound was added to the electrolyte, the battery cycle performance and high temperature storage The performance is obviously improved, indicating that phenyl anhydride can form a film on the surface of the positive electrode material, reduce the direct contact between the electrolyte and the positive electrode, reduce the oxidation and decomposition reaction of the electrolyte, and improve the performance of the battery.

Combined with the results of Figure 6, Figure 7 and Table 1, it shows that: S6 is compared with SD6, S7 is compared with SD7, and stabilizers triphenyl phosphite and dicyclohexylcarbodiimide are added to the electrolyte, and the cycle performance and high temperature storage are significantly improved. Improvement, indicating that triphenyl phosphite and dicyclohexylcarbodiimide can inhibit the side reaction decomposition of the electrolyte and improve battery performance.

Combined with the results of Figure 8, Figure 9 and Table 1, it shows that: compared with S8 and SD8, and compared with S9 and SD9, the wetting agents tristearin and triolein were added to the electrolyte, and the cycle performance was significantly improved, indicating that the three hard Fatty acid glycerides and triglycerides can improve the wettability of the electrolyte to the pole piece and improve the performance of the battery.

Combined with the results of Figure 10 and Table 1, it is shown that: comparing S1 with DS10, it can be seen that triphenyl phosphite and dicyclohexylcarbodiimide are more effective as electrolyte stabilizers; comparing S1 with DS11 and DS12, it can be seen that tristearic acid glycerin Esters and triolein are better as wetting agents;

It can be known from the above analysis that there is a combination of phenyl anhydride and wetting agent in the electrolyte of the present invention, and the phenyl anhydride additive can form a protective film on the surface of the positive electrode material to protect the positive electrode material from damage during high temperature storage and circulation; The wetting agent can make the electrolyte fully wet the pole piece, thereby improving the cycle performance. In addition, there are negative film-forming additives and stabilizers in the electrolyte. These four types of additive components cooperate with each other and are an organic whole, which can more effectively improve the cycle performance and high-temperature performance of the 5V high-voltage lithium secondary battery.

The above-mentioned embodiments only express the implementation manner of the present invention, and the description thereof is relatively specific and detailed, but should not be construed as limiting the patent scope of the invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent for the present invention should be based on the appended claims.

Claims (8)

1. An electrolyte for a 5V high-voltage lithium secondary battery, comprising a negative electrode film-forming additive, an electrolyte stabilizer, an electrolyte lithium salt and a non-aqueous organic solvent, characterized in that said electrolyte also includes a positive electrode film-forming additive and wetting agent. 2. The electrolyte solution for a 5V high-voltage lithium secondary battery according to claim 1, wherein the positive electrode film-forming additive is composed of phenyl anhydrides, which account for 1 to 3% of the total mass of the electrolyte , the phenyl anhydrides are selected from one or more of the following structural formulas: Wherein, R ₁ , R ₂ , R ₃ , R ₄ and R ₅ are independently selected from hydrogen or methyl. 3. the 5V high-voltage lithium secondary battery electrolyte according to claim 1, is characterized in that, described wetting agent is made up of one or both in glyceryl tristearate, glycerol trioleate , which accounts for 0.1-0.5% of the total mass of the electrolyte. 4. the electrolytic solution for 5V high-voltage lithium secondary battery according to claim 1, is characterized in that, described negative electrode film-forming additive is made of fluorinated ethylene carbonate, vinylene carbonate, ethylene carbonate One or more compositions, which account for 1-15% of the total mass of the electrolyte. 5. the 5V high-voltage lithium secondary battery electrolyte according to claim 1, is characterized in that, described electrolyte stabilizer is by a kind of in triphenyl phosphite, dicyclohexylcarbodiimide or Two compositions, which account for 0.01-0.1% of the total mass of the electrolyte. 6. The electrolytic solution for a 5V high-voltage lithium secondary battery according to claim 1, wherein said electrolyte lithium salt is lithium hexafluorophosphate, lithium perchlorate, lithium bisfluorosulfonimide, hexafluoroarsenic acid Any one of lithium, which accounts for 10-17% of the total mass of the electrolyte. 7. 5V high-voltage lithium secondary battery electrolytic solution according to claim 1 is characterized in that, described nonaqueous organic solvent is made of ethyl methanesulfonate (EMS), sulfolane (TMS), normal sulfolane (BS), Ethylene Carbonate (EC), Propylene Carbonate (PC), Dimethyl Carbonate (DMC), Ethyl Methyl Carbonate (EMC), Ethyl Acetate (EA), Propyl Acetate (PA), Propionic Acid Various compositions in ethyl ester (EP), which account for 65-80% of the total mass of the electrolyte. 8. A 5V high-voltage lithium secondary battery, comprising the positive electrode material being one of lithium nickel manganese oxide, lithium cobalt phosphate, and lithium manganese phosphate, and the negative electrode material being one of lithium titanate, graphite, and silicon carbon. It is characterized in that the electrolyte solution of the lithium secondary battery is any electrolyte solution as described in claims 1-7.