CN110620262A - High-voltage lithium ion battery flame retardant, electrolyte and battery - Google Patents

Abstract

The invention discloses a high-voltage lithium ion battery flame retardant, electrolyte and a battery thereof. The high-voltage lithium ion battery flame retardant provided by the invention is a perfluorinated or mostly fluorinated sulfonyl compound, has an antioxidant property, is relatively stable under high voltage, does not influence the performance of the lithium ion battery, can inhibit the chain reaction of hydroxyl radicals or hydrogen radicals, reduces the flammability of electrolyte, and simultaneously generates SO (sulfur oxide) by decomposing the flame retardant when the battery is combusted₂Also can obstruct air, lead the battery to be self-extinguished, effectively improve the electrochemical and thermodynamic stability of the lithium ion battery, further improve the safety of the high-voltage lithium ion battery, and has the advantages of small addition, low cost, simple synthesis and the like, is easy to realize, is beneficial to widely pushingHas wide application.

Description

High-voltage lithium-ion battery flame retardant, electrolyte and battery thereof

technical field

The invention belongs to the technical field of lithium-ion batteries, and in particular relates to a high-voltage lithium-ion battery flame retardant, an electrolyte and a battery thereof.

Background technique

The use of traditional fossil fuels will release a large amount of harmful gases such as carbon dioxide, sulfides, nitrogen compounds and dust, causing greenhouse effect and polluting the environment. At the same time, with the gradual depletion of these traditional fossil fuels, the development and utilization of renewable clean energy potential It must be done. Clean energy includes water energy, solar energy, wind energy, tidal energy and nuclear energy, which are renewable energy. Through intermediate conversion, that is, using energy storage devices, these energies can be utilized in the form of electric energy-other forms of energy-electric energy. Lithium-ion batteries in energy storage devices have high voltage, high energy density, long life and high safety. The advantages have received a lot of attention, and it has developed rapidly in the fields of portable electronic products, large-scale power supplies, and energy storage power stations. The rapid development of the application field puts forward higher requirements for high power, high safety, long life and low cost of lithium-ion batteries. High-voltage spinel lithium nickel manganese oxide has a high voltage platform of up to 4.7V (Vs Li). The high operating voltage can greatly reduce the BMS management cost and safety of the battery, and the spinel lithium nickel manganese oxide has a three-dimensional The lithium ion channel has the advantages of high power, and lithium nickel manganese oxide does not contain the rare resource Co, and the cost is low. It is a very good next-generation positive electrode battery material.

The safety of lithium-ion batteries has always been a concern for everyone. However, since the current lithium-ion batteries mostly use extremely flammable carbonate-based organic electrolytes, overcharging, overdischarging and overheating of the battery may cause the battery to burn or even explode. Adding a flame retardant to the electrolyte can reduce the flammability of the electrolyte, but under high pressure, common electrolyte flame retardants will undergo oxidative decomposition, thereby affecting the electrochemical performance of lithium-ion batteries.

Contents of the invention

In view of the above deficiencies, one of the objectives of the present invention is to provide a high-voltage lithium-ion battery flame retardant that does not oxidize and decompose under high pressure, does not affect battery performance, and improves the electrochemical stability and thermodynamic stability of the battery.

The second object of the present invention is to provide a high-voltage lithium-ion battery electrolyte containing the above-mentioned high-voltage lithium-ion battery flame retardant.

The third object of the present invention is to provide a lithium-ion battery containing the electrolyte solution of the above-mentioned high-voltage lithium-ion battery.

To achieve the above object, the technical solution provided by the present invention is:

A high-voltage lithium-ion battery flame retardant is a perfluorinated or mostly fluorinated sulfonyl compound. Oxidation and decomposition will not occur during the cycle of high-voltage lithium batteries, and will not affect the cycle performance of the battery. At the same time, when the battery burns, the SO2 produced by the decomposition of the flame retardant will also block the air, make the battery self _- extinguishing, improve the electrochemical and thermodynamic stability of the high-voltage lithium battery, and then improve the safety of the high-voltage lithium battery.

As an improvement of the present invention, its fluorination degree is 60-100%.

As an improvement of the present invention, it contains a sulfonyl functional group, and its structural formula is as follows:

R in the structural formula is selected from perfluorinated or partially fluorinated ester groups, phenyl, cyano, alkenyl and halogen atoms, and R2 is selected from perfluorinated or partially fluorinated _compounds containing ₁ to 10 carbon atoms Substituted alkyl.

As an improvement of the present invention, it is selected from perfluoro-1-octane sulfonyl fluoride, perfluorobutyl sulfonyl fluoride, N-ethyl perfluoro octane sulfonamide, perfluorobutyl sulfonate, Perfluorooctanesulfonyl chloride, Perfluorophenyl 3-(pyridin-2-yldisulfonyl)propionate, Perfluoro(4-methyl-3,6-dioxocta-7-ene)-sulfonyl Fluorine, perfluorohexylsulfonyl fluoride, perfluorophenyl 4-methyl-4-(pyridin-2-yldisulfonyl)valerate, lithium fluorosulfonyldifluoroacetate, pentafluorobenzenesulfonyl chloride, 2, One or more of 2,3,3,4,4-hexafluoropentane-1,5-diylbis(4-methylbenzenesulfonate).

A high-voltage lithium-ion battery electrolyte, which is composed of additives, lithium salts, organic solvents and the high-voltage lithium-ion battery flame retardant described in any one of claims 1 to 4, the high-voltage lithium-ion battery flame retardant The addition ratio in the lithium-ion battery electrolyte is 0.1%-15% by mass.

As an improvement of the present invention, said additive also includes other functional additives, said other functional additives are selected from fluoroethylene carbonate (FEC), 1,3-propanediol cyclosulfate (PCS), vinylene carbonate ( VC), vinyl sulfite (ES), dimethyl sulfite (DMS), (trimethylsilyl) phosphite or one or more.

As an improvement of the present invention, the organic solvent is selected from propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), diethyl carbonate (DEC), dimethyl carbonate (DMC ), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC), dioxolane (DOL), 1,2-dimethoxyethane (DME), tetrahydrofuran (THF), 2-methyltetrahydrofuran One or more of (2Me-THF), γ-butyrolactone (BL), methyl acetate (MA), ethyl acetate (EA), dimethyl sulfoxide (DMSO), sulfolane (SL) Mixed solvents in any proportion.

As an improvement of the present invention, the lithium salt is lithium tetrafluoroborate, lithium hexafluorophosphate, lithium perchlorate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethylsulfonyl)imide, tris(trifluoromethylsulfonyl)imide, One or more of methylsulfonyl)methyllithium, lithium bisoxalate borate, lithium difluorooxalate borate or lithium tetrafluorooxalate phosphate, the molar concentration range of the lithium salt in the high-voltage lithium-ion battery electrolyte is 0.5～3mol/L.

A lithium-ion battery comprising a positive electrode, a negative electrode, a separator and the high-voltage lithium-ion battery electrolyte according to any one of claims 5-8.

As an improvement of the present invention, its charging cut-off voltage is 4.7-5V. The positive electrode active material of the lithium ion battery is high-voltage spinel lithium nickel manganese oxide.

The beneficial effects of the present invention are: the high-voltage lithium-ion battery flame retardant provided by the present invention is a perfluorinated or mostly fluorinated sulfonyl compound, has anti-oxidation properties, is relatively stable under high pressure, and does not affect the life of the lithium-ion battery. performance, can also inhibit the chain reaction of hydroxyl radicals or hydrogen radicals, reduce the flammability of the electrolyte, and at the same time when the battery burns, the SO ₂ produced by the decomposition of the flame retardant will also block the air, making the battery self-extinguishing, effectively improving The electrochemical and thermodynamic stability of the lithium-ion battery can further improve the safety of the high-voltage lithium-ion battery, and it has the advantages of small addition, low cost and simple synthesis, and is easy to realize, which is conducive to wide application.

Below in conjunction with embodiment, the present invention will be further described.

Detailed ways

Example 1:

Preparation of high-voltage lithium-ion battery electrolyte:

In a glove box filled with argon (moisture <10ppm, oxygen <1ppm), mix ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate in a mass ratio of 1:1:1, and add mass Perfluoro-1-octanesulfonyl fluoride with a fraction of 3%, and then slowly add lithium salt LiPF ₆ at a concentration of 1 mol/L, and stir until it is completely dissolved to obtain electrolyte A1 for a high-voltage lithium-ion battery.

Preparation of lithium-ion batteries:

LiNi _0.5 Mn _1.5 O ₄ (LNMO) is used as the positive electrode active material, carbon black is used as the conductive additive, and carboxymethyl cellulose (CMC), styrene-butadiene copolymer (SBR) is used as the binder, according to the mass The ratio is 92:5:1:2, mixed in water evenly, coated on the aluminum foil current collector, dried, cold pressed, cut into discs with a diameter of φ14mm, and placed in the glove box.

Graphite is used as the negative electrode active material, carbon black is used as the conductive additive, and the copolymer (SBR) of carboxymethylcellulose (CMC) and styrene and butadiene is used as the binder, according to the mass ratio of 93:2:2: 3 After mixing evenly in water, coat the copper foil current collector, dry, cold press, cut into discs with a diameter of φ15mm, and place them in the glove box.

Polyethylene (PE) was used as the base film (12 μm) and a nano-alumina coating (2 μm) was coated on both sides of the base film as a separator.

The positive pole piece, the separator, and the negative pole piece are placed in order, and the prepared electrolyte is injected, and then packaged and assembled into a button battery with a model number of CR2032. After the prepared button battery was left to stand at room temperature for 24 hours, the battery was subjected to a cycle test using a blue battery charge and discharge tester (purchased from Wuhan Landian Electronics Co., Ltd.).

Example 2:

Its difference from Example 1 is the preparation of high-voltage lithium-ion battery electrolyte:

In a glove box filled with argon (moisture <10ppm, oxygen <1ppm), mix ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate in a mass ratio of 1:1:1, and add mass Fraction of 15% perfluorobutyl sulfonyl fluoride, 5% N-ethyl perfluorooctyl sulfonamide, and then slowly add lithium salt LiPF ₆ , the concentration of the salt is 1mol/L, and stir until it is completely dissolved to obtain High-voltage lithium-ion battery electrolyte A2.

Example 3:

Its difference from Example 1 is the preparation of high-voltage lithium-ion battery electrolyte:

In a glove box filled with argon (moisture <10ppm, oxygen <1ppm), mix ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate in a mass ratio of 1:1:1, and add mass Perfluorobutanesulfonate with a fraction of 0.1% was added slowly to lithium salt LiPF ₆ at a concentration of 1 mol/L, and stirred until it was completely dissolved to obtain electrolyte A3 for a high-voltage lithium-ion battery.

Example 4:

Its difference from Example 1 is the preparation of high-voltage lithium-ion battery electrolyte:

In a glove box filled with argon (moisture <10ppm, oxygen <1ppm), mix ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate in a mass ratio of 1:1:1, and add mass The fraction is 5% perfluorooctanesulfonyl chloride, 5% perfluorophenyl 3-(pyridin-2-yldisulfonyl) propionate, then slowly add lithium salt LiPF ₆ , the salt concentration is 1mol/L , and stirred until it was completely dissolved to obtain high-voltage lithium-ion battery electrolyte A4.

Example 5:

Its difference from Example 1 is the preparation of high-voltage lithium-ion battery electrolyte:

In a glove box filled with argon (moisture <10ppm, oxygen <1ppm), mix ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate in a mass ratio of 1:1:1, and add mass Perfluoro(4-methyl-3,6-dioxocta-7-ene)-sulfonyl fluoride with a fraction of 2%, then slowly add lithium salt LiPF ₆ , the concentration of the salt is 1mol/L, and stir until it is completely Dissolved to obtain high-voltage lithium-ion battery electrolyte A5.

Embodiment 6:

Its difference from Example 1 is the preparation of high-voltage lithium-ion battery electrolyte:

In a glove box filled with argon (moisture <10ppm, oxygen <1ppm), mix ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate in a mass ratio of 1:1:1, and add mass The fraction is 3% perfluorohexylsulfonyl fluoride, 5% perfluorophenyl 4-methyl-4-(pyridin-2-yl disulfonyl) pentanoate, then slowly add lithium salt LiPF ₆ , salt The concentration is 1mol/L, and stirred until it is completely dissolved to obtain electrolyte solution A6 for a high-voltage lithium-ion battery.

Embodiment 7:

Its difference from Example 1 is the preparation of high-voltage lithium-ion battery flame retardant:

In a glove box filled with argon (moisture <10ppm, oxygen <1ppm), mix ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate in a mass ratio of 1:1:1, and add mass The fraction is 5% of pentafluorobenzenesulfonyl chloride, 5% of 2,2,3,3,4,4-hexafluoropentane-1,5-diylbis(4-methylbenzenesulfonate), and Slowly add lithium salt LiPF ₆ with a salt concentration of 1 mol/L, and stir until it is completely dissolved to obtain high-voltage lithium-ion battery electrolyte A7.

Embodiment 8:

Its difference from Example 1 is the preparation of high-voltage lithium-ion battery flame retardant:

In a glove box filled with argon (moisture <10ppm, oxygen <1ppm), mix ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate in a mass ratio of 1:1:1, and add mass The fraction is 3% perfluoro-1-octanesulfonyl fluoride, 0.5% vinylene carbonate, 2% fluoroethylene carbonate (FEC), then slowly add lithium salt LiPF ₆ , the salt concentration is 1mol/ L was stirred until it was completely dissolved to obtain high-voltage lithium-ion battery electrolyte A8.

Embodiment 9:

Its difference from Example 1 is the preparation of high-voltage lithium-ion battery flame retardant:

In a glove box filled with argon (moisture <10ppm, oxygen <1ppm), mix ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate in a mass ratio of 1:1:1, and add mass A fraction of 2% perfluoro(4-methyl-3,6-dioxocta-7-ene)-sulfonyl fluoride, 1% 1,3-propanediol cyclic sulfate, 1% vinyl sulfite, and Slowly add lithium salt LiPF ₆ with a salt concentration of 1 mol/L, and stir until it is completely dissolved to obtain lithium ion battery electrolyte A9.

Comparative example 1:

Its difference from Example 1 is the preparation of electrolyte:

In a glove box filled with argon (moisture <10ppm, oxygen <1ppm), mix ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate in a mass ratio of 1:1:1, and then slowly add lithium salt LiPF _6. The concentration of the salt is 1 mol/L, and stirred until it is completely dissolved to obtain the lithium-ion battery electrolyte B1.

Comparative example 2:

In a glove box filled with argon (moisture <10ppm, oxygen <1ppm), mix ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate in a mass ratio of 1:1:1, and add mass Ethyl methanesulfonyl acetate with a fraction of 0.1% was added slowly to lithium salt LiPF ₆ at a concentration of 1 mol/L, and stirred until it was completely dissolved to obtain electrolyte solution B2 for lithium ion batteries.

Comparative example 3:

Its difference from Example 1 is the preparation of electrolyte:

In a glove box filled with argon (moisture <10ppm, oxygen <1ppm), mix ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate in a mass ratio of 1:1:1, and add mass The fraction is 10% of 4-acetylbenzenesulfonyl chloride, then slowly add lithium salt LiPF ₆ , the concentration of the salt is 1mol/L, stir until it is completely dissolved, and obtain lithium ion battery electrolyte B3.

Comparative example 4:

In a glove box filled with argon (moisture <10ppm, oxygen <1ppm), mix ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate in a mass ratio of 1:1:1, and add mass 1% tert-butylsulfinamide, and slowly add lithium salt LiPF ₆ at a concentration of 1 mol/L, and stir until it is completely dissolved to obtain lithium ion battery electrolyte B4.

Comparative example 5:

Its difference from Example 1 is the preparation of electrolyte:

In a glove box filled with argon (moisture <10ppm, oxygen <1ppm), mix ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate in a mass ratio of 1:1:1, and add mass Isopropylsulfamoyl chloride with a fraction of 2%, and then slowly add lithium salt LiPF ₆ at a concentration of 1 mol/L, and stir until it is completely dissolved to obtain lithium ion battery electrolyte B5.

Table 1 shows the test results of the battery room temperature and high temperature cycle performance of the comparative examples and examples.

Table 1

battery number 100-week capacity retention (%) Average efficiency (%) Comparative example 1 71 99.3 Comparative example 2 55 98.2 Comparative example 3 30 97.0 Comparative example 4 50 98.1 Comparative example 5 53 98.3 Example 1 76 99.4 Example 2 75 99.3 Example 3 71 99.3 Example 4 74 99.3 Example 5 73 99.3 Example 6 75 99.4 Example 7 72 99.3 Example 8 86 98.6 Example 9 87 98.5

It can be seen from the test results in Table 1 that:

Comparing the comparative examples, it can be seen that when using unfluorinated or low-fluorinated sulfonyl compounds as flame retardants, these flame retardants will decompose under high pressure, which will seriously affect the electrochemical cycle performance of the battery, and the efficiency and efficiency of the battery. The capacity retention rate has a large decrease, indicating that the unfluorinated or low-fluorinated sulfonyl compounds are not suitable as flame retardants for high-voltage lithium-ion batteries.

As can be seen from the examples, when the perfluorinated or partly fluorinated sulfonyl compounds of the present invention are used as flame retardants, the efficiency of the battery is not reduced, and some flame retardant additives can also slightly increase the efficiency of the battery. The capacity retention rate shows that the high-voltage lithium-ion battery flame retardant described in the present invention also has a gaining effect on the battery.

Table 2 is a comparison of the self-extinguishing time of the electrolytes of the comparative examples and the examples.

Table 2

Electrolyte number Flame retardant content (%) Self-extinguishing time (s/g) A1 3 72 A2 15 55 A3 0.1 77 A4 10 65 A5 2 75 A6 8 66 A7 10 63 A8 3 71 A9 2 70 B1 0 83 B2 0.1 79 B3 10 73 B4 1 76 B5 2 75

It can be seen from Table 2 that after adding the flame retardant for high-voltage lithium-ion batteries of the present invention, the self-extinguishing time of the electrolyte is significantly reduced, and with the increase of the content, the shorter the self-extinguishing time, When the battery flame retardant is added at 15%, the self-extinguishing time of the electrolyte is reduced from 83 s/g to 55 s/g, a decrease of 28 s/g, and the effect is very significant. It can be seen from the comparative examples that when unfluorinated or low-fluorinated sulfonyl compounds are used as flame retardants, the effect of self-extinguishing is far less than that of the high-voltage lithium ion compound described in the present invention when the same amount is added. Battery flame retardant.

The above-mentioned embodiments are only preferred implementation modes of the present invention, and the present invention cannot enumerate all the implementation modes one by one. All technical solutions using one of the above-mentioned embodiments, or equivalent changes made according to the above-mentioned embodiments, are included in this document. within the scope of invention protection.

According to the disclosure and teaching of the above specification, those skilled in the art to which the present invention pertains can also make changes and modifications to the above embodiment. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention. In addition, although some specific terms are used in this specification, these terms are only for convenience of description and do not constitute any limitation to the present invention. As described in the above embodiments of the present invention, other flame retardants, electrolytes and batteries obtained by using the same or similar methods and components are within the protection scope of the present invention.

Claims (10)

1. A high-voltage lithium-ion battery flame retardant, characterized in that it is a perfluorinated or most fluorinated sulfonyl compound. 2. The high-voltage lithium-ion battery flame retardant according to claim 1, characterized in that its fluorination degree is 60-100%. 3. The high-voltage lithium-ion battery flame retardant according to claim 1, wherein it contains a sulfonyl functional group, and its structural formula is as follows: R in the structural formula is selected from perfluorinated or partially fluorinated ester groups, phenyl, cyano, alkenyl and halogen atoms, and R2 is selected from perfluorinated or partially fluorinated _compounds containing ₁ to 10 carbon atoms Substituted alkyl. 4. The high-voltage lithium-ion battery flame retardant according to claim 1, characterized in that, it is selected from perfluoro-1-octanesulfonyl fluoride, perfluorobutylsulfonyl fluoride, N-ethyl perfluoro n-octanesulfonamide, perfluorobutanesulfonate, perfluorooctanesulfonyl chloride, perfluorophenyl 3-(pyridin-2-yldisulfonyl)propionate, perfluoro(4-methyl-3, 6-dioxocta-7-ene)-sulfonyl fluoride, perfluorohexylsulfonyl fluoride, perfluorophenyl 4-methyl-4-(pyridin-2-yldisulfonyl)valerate, fluorosulfonyl One or more of lithium difluoroacetate, pentafluorobenzenesulfonyl chloride, 2,2,3,3,4,4-hexafluoropentane-1,5-diylbis(4-methylbenzenesulfonate) kind. 5. A high-voltage lithium-ion battery electrolyte, characterized in that it is composed of additives, lithium salts, organic solvents and the high-voltage lithium-ion battery flame retardant described in any one of claims 1 to 4, the high-voltage lithium-ion battery The addition ratio of the battery flame retardant in the high-voltage lithium-ion battery electrolyte is 0.1% to 15% by mass. 6. The high-voltage lithium-ion battery electrolyte according to claim 5, wherein the additive also includes other functional additives, and the other functional additives are selected from fluoroethylene carbonate, 1,3-propanediol cyclic sulfate , one or more of vinylene carbonate, vinyl sulfite, dimethyl sulfite, (trimethylsilyl) phosphite. 7. The high-voltage lithium-ion battery electrolyte according to claim 5, wherein the organic solvent is selected from propylene carbonate, ethylene carbonate, butylene carbonate, diethyl carbonate, dimethyl carbonate, carbonic acid Methyl ethyl ester, methyl propyl carbonate, dioxolane, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, methyl acetate, ethyl acetate, dimethyl A mixed solvent in which one or more of sulfoxide and sulfolane are mixed in any proportion. 8. The high-voltage lithium-ion battery electrolyte according to claim 5, wherein the lithium salt is lithium tetrafluoroborate, lithium hexafluorophosphate, lithium perchlorate, lithium trifluoromethanesulfonate, bis(trifluoromethane One or more of lithium sulfonyl imide, lithium tris(trifluoromethylsulfonyl)methyl, lithium bisoxalate borate, lithium difluorooxalate borate or lithium tetrafluorooxalate phosphate, the lithium salt is in The molar concentration range in the high-voltage lithium-ion battery electrolyte is 0.5-3 mol/L. 9. A lithium-ion battery, characterized in that it comprises a positive pole, a negative pole, a diaphragm and the high-voltage lithium-ion battery electrolyte according to any one of claims 5-8. 10. The lithium-ion battery according to claim 9, characterized in that its charging cut-off voltage is 4.7-5V.