Lithium ion battery electrolyte additive, electrolyte and lithium ion battery thereof

Abstract

The present application relates to the technical field of lithium ion battery, in particular to a kind of lithium ion battery electrolyte additive and its electrolyte and lithium ion battery, the additive structural formula is as follows: Wherein, Ar is selected from any one of phenyl, pyridyl or quinoline group;R1, R2 Same or different, R1 And R2 respectively independently selected from any one of hydrogen, fluorine, cyano, C1~C5 Alkyl, C1~C4 Alkoxy, fluorine-containing C1~C4 Alkoxy, x is selected from 1, 2 or 3;Y, z respectively selected from 1, 2, 3 or 4, x+y+z≤6, and Ar is phenyl, x=1, R1 And R2 are not hydrogen simultaneously.The additive can form stable SEI film on the negative electrode surface, reduce the impedance of battery, improve the low temperature performance of battery, and also have flame-retardant function.

Description

Technical Field

[0001] This invention relates to a lithium-ion battery electrolyte additive, its electrolyte, and a lithium-ion battery, belonging to the field of lithium-ion battery technology. Background Technology

[0002] Lithium-ion batteries, due to their high energy density, high power output, long lifespan, and environmental friendliness, as well as the huge demand in the electronics industry and the potential vast market in electric vehicles, space technology, and defense, have become one of the high-tech green products that countries around the world are vying to develop. However, lithium-ion batteries also have their own weaknesses. Lithium-ion electrolytes are mostly composed of organic solvents and conductive lithium salts. Commonly used organic solvents are alkyl carbonate compounds, such as diethyl carbonate (DEC) and ethylene carbonate (EC), which are all flammable compounds. Improper battery use (overcharging, short circuits, etc.) can easily lead to overheating, causing the electrolyte to burn, resulting in fires or even explosions. Therefore, given that the main battery materials (including electrode materials, electrolyte materials, and separator materials) cannot be replaced in the short term, improving the flame retardancy of lithium-ion electrolytes is an effective way to enhance the safety of lithium-ion batteries.

[0003] In addition, during the charging state, lithium-ion batteries undergo partial oxidation and decomposition at the interface between the positive electrode material and the non-aqueous electrolyte. As a result, the decomposition products generated hinder the original electrochemical reaction of the battery, leading to a decline in battery performance such as cycle characteristics.

[0004] Currently, most lithium-ion batteries use highly flammable organic carbonates as electrolytes. Under extreme conditions (high temperature, overcharge, short circuit, etc.), the electrolyte may ignite, leading to fires or even explosions. Patent application CN114206774A describes lithium difluorophosphate (LiPO2F2) as an excellent lithium salt additive that can significantly improve battery cycle stability at high voltages and low-temperature charging performance. This is because the addition of difluorophosphate slows down the decomposition of lithium hexafluorophosphate, improving the high-voltage stability of the electrolyte. Simultaneously, the SEI formed by this additive contains a significant amount of fluorinated lithium phosphate, which can increase the migration rate of lithium ions, reduce battery impedance, and improve the battery's low-temperature performance. However, this additive has poor solubility and high manufacturing costs, limiting its widespread use. Therefore, developing an electrolyte additive with good solubility, effective improvement in battery safety, cycle life, environmental adaptability, and low cost is of great significance. Summary of the Invention

[0005] This invention addresses the shortcomings of existing technologies by providing a lithium-ion battery electrolyte additive, its electrolyte, and a lithium-ion battery. It can effectively inhibit the decomposition of lithium hexafluorophosphate, improve the thermal and storage stability of LiPF6-containing electrolytes, form a stable SEI film on the negative electrode surface, reduce battery impedance, improve the battery's low-temperature performance, and also has flame-retardant properties.

[0006] The technical solution of this invention to solve the above-mentioned technical problems is as follows: a lithium-ion battery electrolyte additive, wherein the additive has the following structural formula:

[0007]

[0008] Wherein, Ar is selected from any one of phenyl, pyridyl or quinolinyl; R1 and R2 may be the same or different, and R1 and R2 are independently selected from any one of hydrogen, fluorine, cyano, C1-C5 alkyl, C1-C4 alkoxy, and fluorine-containing C1-C4 alkoxy; x is selected from 1, 2 or 3; y and z are selected from 1, 2, 3 or 4 respectively, x+y+z≤6, and Ar is phenyl. When x=1, R1 and R2 are not both hydrogen.

[0009] Furthermore, Ar is selected from any one of phenyl, pyridyl or quinolinyl; R1 and R2 may be the same or different, and R1 and R2 are independently selected from any one of hydrogen, fluorine, cyano, C1-C5 alkyl, C1-C4 alkoxy, and x is selected from 1 or 2; y and z are selected from 1, 2, 3 or 4, x+y+z≤6, and Ar is phenyl. When x=1, R1 and R2 are not both hydrogen.

[0010] Furthermore, the additive is selected from any one or a mixture of the following structures:

[0011]

[0012]

[0013]

[0014]

[0015]

[0016] The present invention also discloses a non-aqueous electrolyte for lithium-ion batteries, wherein the electrolyte comprises a solvent, an electrolyte lithium salt, and an additive, wherein the additive is one or a combination of several of the lithium-ion battery electrolyte additives of the present invention.

[0017] Furthermore, based on the total mass of the electrolyte, the mass content of the additive is 0.01wt% to 10wt%.

[0018] Furthermore, the electrolyte also includes auxiliary additives, which are one or a combination of several of the following: 1,3-propanesulfonyl lactone (PS), 1,4-butanesulfonyl lactone (BS), propenyl-1,3-sulfonyl lactone (PST), vinyl sulfate (DTD), methylene disulfonate (MMDS), vinylene carbonate (VC), fluoroethylene carbonate (FEC), lithium bis(fluorosulfonyl imide) (LiFSI), lithium difluorooxalate borate (LiODFB), lithium difluorooxalate phosphate, lithium difluorophosphate, and lithium tetrafluoroborate.

[0019] Furthermore, based on the total mass of the electrolyte, the mass content of the auxiliary additive is 0.1wt% to 3.0wt%.

[0020] Furthermore, the electrolyte lithium salt is one or a combination of several of LiPF6, LiClO4, LiBF4, LiBOB, LiODFB, LiTDI, LiTFSI and LiFSI.

[0021] Furthermore, based on the total mass of the electrolyte, the content of the electrolyte lithium salt is 10wt% to 20wt%.

[0022] Furthermore, the solvent is one or a combination of several of the following: ethylene carbonate, propylene carbonate, γ-butyrolactone, phenyl acetate, 1,4-butylsulfonyl lactone, 3,3,3-trifluoropropylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, ethyl acetate, methyl propyl carbonate, propyl propionate, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 2,2-difluoroethyl acetate, 2,2-difluoroethyl propionate, and 2,2-difluoroethyl methyl carbonate.

[0023] The present invention also discloses a lithium-ion battery, which includes a negative electrode, a positive electrode, a separator disposed between the negative electrode and the positive electrode, and the non-aqueous electrolyte of the lithium-ion battery of the present invention.

[0024] The beneficial effects of this invention are:

[0025] 1) The nitrogen-containing heterocyclic difluorophosphate provided by the present invention, based on the electron-rich nature of nitrogen atoms, can effectively neutralize free acidic substances in the electrolyte, thereby inhibiting the decomposition of lithium hexafluorophosphate and thus improving the thermal stability and storage stability of lithium hexafluorophosphate.

[0026] 2) The difluorophosphate ester described in this invention can work together with VC to reduce on the negative electrode surface and generate a low-impedance interface film. This interface film is mainly composed of LiF and PO compounds, which will further modify the electrolyte interface film induced by VC, making the ionic conductivity of the SEI film on the graphite surface stronger, thereby reducing battery impedance and improving battery cycle performance.

[0027] 3) The difluorophosphate described in this invention has significantly improved electrochemical redox stability due to the increased fluorine atom content, and the synergistic flame retardant effect of fluorine and phosphorus can further improve the flame retardant efficiency. Attached Figure Description

[0028] Figure 1 As described in Example 1, A01 1 H-NMR spectrum. Detailed Implementation

[0029] The specific embodiments of the present invention will be described in detail below. The present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used is for describing particular embodiments only and is not intended to limit the invention.

[0031] I. Synthesis Examples

[0032] Synthesis Example 1: Synthesis of Compound A01

[0033] Step 1: Synthesis of Intermediate 1

[0034]

[0035] 11.0 g (0.10 mol) hydroquinone (starting material 1), 25.3 g (0.25 mol) triethylamine, and 200.0 g dichloromethane were added to a 500 mL three-necked flask. The internal temperature was controlled at 0–10 °C. 38.3 g (0.25 mol) phosphorus oxychloride (starting material 2) was added dropwise. The system was kept at 10–20 °C and stirred for 2 hours. After removing the solvent, 30.7 g of light brown solid (intermediate 1) was obtained, with a GC purity of 96.63% and a yield of 89.24%.

[0036] Step 2: Synthesis of target substance A01

[0037]

[0038] 17.2 g (0.05 mol) of intermediate 1, 13.1 g (0.225 mol) of potassium fluoride (starting material 3), 0.64 g (0.002 mol) of tetrabutylammonium bromide, and 150.0 g of DMF were added to a 500 mL three-necked flask and incubated at 110 °C for 8 hours. The mixture was filtered, and the filtrate was desolventized to give 12.1 g of an off-white solid with a GC purity of 89.42% and a yield of 87.05%. The crude product was washed with water and subjected to column chromatography to give 8.8 g of the target compound A01 with a GC purity of 99.75% and a yield of 63.31%.

[0039] GC-MS: 278, 1H NMR (400MHz): solvent deuterated chloroform, δ (ppm): 7.501 ppm (s, 4H)

[0040] Synthesis Example 2: Synthesis of Compound A23

[0041] Step 1: Synthesis of Intermediate 1

[0042]

[0043] 47.6 g (0.5 mol) of 4-hydroxypyridine (starting material 1), 75.9 g (0.75 mol) of triethylamine, and 900.0 g of dichloromethane were added to a 2 L three-necked flask. The internal temperature was controlled at 0–10 °C. 115.0 g (0.75 mol) of phosphorus oxychloride (starting material 2) was added dropwise. The system was kept at 5–10 °C and stirred for 4.5 hrs. After solvent removal, 91.0 g of a light brown liquid was obtained, with a GC purity of 91.55% and a yield of 85.85%. The crude product was distilled under reduced pressure to obtain 77.3 g of intermediate 1, with a GC purity of 99.33% and a yield of 72.92%.

[0044] Step 2: Synthesis of target compound A23

[0045]

[0046] 42.4 g (0.2 mol) of intermediate 1, 29.1 g (0.5 mol) of potassium fluoride (raw material 3), 3.2 g (0.01 mol) of tetrabutylammonium bromide, and 300.0 g of DMF were added to a 1 L three-necked flask and kept at 90 °C for 7 hours. The mixture was then filtered, and the filtrate was desolventized to give 32.1 g of a brown liquid with a GC purity of 89.42% and a yield of 89.66%. The crude product was distilled under reduced pressure to give 25.4 g of the target compound A23 with a GC purity of 99.75% and a yield of 70.95%.

[0047] GC-MS: 179, 1H NMR (400MHz): solvent deuterated chloroform, δ (ppm): 8.486–8.463 ppm (dd, 2H), 7.501–7.476 ppm (dd, 2H)

[0048] Synthesis Example 3: Synthesis of Compound A27

[0049] Step 1: Synthesis of Intermediate 1

[0050]

[0051] 60.1 g (0.50 mol) of 2-cyano-4-hydroxypyridine (starting material 1), 75.9 g (0.75 mol) of triethylamine, and 1000.0 g of dichloromethane were added to a 2 L three-necked flask. The internal temperature was controlled at 5–10 °C. 115.0 g (0.75 mol) of phosphorus oxychloride (starting material 2) was added dropwise. The system was kept at 10–20 °C and stirred for 3 hours. After solvent removal, 98.4 g of a brown liquid was obtained with a GC purity of 88.17% and a yield of 83.04%. The crude product was distilled under reduced pressure to obtain 82.6 g of intermediate 1 with a GC purity of 99.29% and a yield of 69.7%.

[0052] Step 2: Synthesis of target compound A27

[0053]

[0054] 47.4 g (0.2 mol) of intermediate 1, 29.1 g (0.50 mol) of potassium fluoride (raw material 3), 3.2 g (0.01 mol) of tetrabutylammonium bromide, and 500.0 g of DMF were added to a 1 L three-necked flask and kept at 100 °C for 4 hours. The mixture was then filtered, and the filtrate was desolventized to give 36.4 g of a brown liquid with a GC purity of 87.06% and a yield of 89.22%. The crude product was distilled under reduced pressure to give 29.2 g of the target compound A27 with a GC purity of 99.62% and a yield of 71.57%.

[0055] GC-MS: 204, 1H NMR (400MHz): solvent deuterated chloroform, δ (ppm): 8.782–8.764 ppm (d, 1H), 8.395–8.372 ppm (dd, 1H), 8.139–8.135 ppm (dd, 1H)

[0056] Synthesis Example 4: Synthesis of Compound A28

[0057] Step 1: Synthesis of Intermediate 1

[0058]

[0059] 14.5 g (0.10 mol) of 8-hydroxyquinoline (starting material 1), 15.2 g (0.15 mol) of triethylamine, and 200.0 g of dichloromethane were added to a 500 mL three-necked flask. The internal temperature was controlled at -10 to 0 °C. 23.0 g (0.15 mol) of phosphorus oxychloride (starting material 2) was added dropwise. The system was kept at 10 to 20 °C and stirred for 2.5 hrs. After removing the solvent, 22.5 g of a light brown solid (intermediate 1) was obtained with a GC purity of 95.97% and a yield of 85.88%.

[0060] Step 2: Synthesis of target compound A28

[0061]

[0062] 13.1 g (0.05 mol) of intermediate 1, 7.3 g (0.125 mol) of potassium fluoride (starting material 3), 0.16 g (0.0005 mol) of tetrabutylammonium bromide, and 65.0 g of DMF were added to a 250 mL three-necked flask and incubated at 130 °C for 5 hours. The mixture was filtered, and the filtrate was desolventized to give 10.1 g of an off-white solid with a GC purity of 85.44% and a yield of 87.83%. The crude product was washed with water and subjected to column chromatography to give 7.9 g of the target compound A28 with a GC purity of 99.86% and a yield of 68.70%.

[0063] GC-MS: 229, 1H NMR (400MHz): solvent deuterated chloroform, δ (ppm): 8.955~6.795ppm (m, 6H)

[0064] II. Preparation of Non-Aqueous Electrolyte for Lithium-ion Batteries

[0065] Example 1

[0066] In a glove box with a nitrogen atmosphere containing less than 1 ppm of water, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and propyl propionate (PP) organic solvents are mixed in proportion. LiPF6 is dissolved in the organic solvents. Electrolyte additives and other additives are then added to the organic solvents. The additives and electrolyte lithium salt are completely dissolved and mixed evenly to obtain a non-aqueous electrolyte for lithium-ion batteries.

[0067] EC has a low freezing point and needs to be preheated to 50°C on an electric magnetic stirrer to melt. The content of the electrolyte lithium salt LiPF6 is 13.5 wt% of the total electrolyte weight. The weight ratio of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and propyl propionate (PP) is EC:EMC:PP = 30:50:20. The amount of electrolyte additive is 1.0 wt% of the total electrolyte weight. In this embodiment, the electrolyte additive is the A16 compound provided by this invention. Other additives are vinylene carbonate (VC), and the amount of other additives is 2.0 wt% of the total electrolyte weight.

[0068] The ionic conductivity of the lithium-ion battery non-aqueous electrolyte obtained in this embodiment was measured at 25°C using an ionic conductivity measuring device (Bio-Logic, France, model: VSP), and the result was 6.83 mS / cm. Then, the peak of the LiPF6 decomposition product was determined using 19F-NMR (model: JNM-ECZ400S, 400MHz) with deuterated acetone solvent (internal standard: trifluoromethylbenzene). The integral ratio of the LiPF6 decomposition product peak to the LiPF6 peak was observed to be less than 0.1%.

[0069] Furthermore, the non-aqueous electrolyte for lithium-ion batteries obtained in this embodiment was heated at 80°C for 240 hours. After heating, the liquid turned pale yellow, and the ionic conductivity at 25°C was measured, showing a result of 6.81 mS / cm, with a retention rate of 99.71% for ionic conductivity. Then, the peak of the LiPF6 decomposition product was determined by 19F-NMR, with an integral ratio of 0.16% relative to LiPF6. The relevant data results are shown in Table 1.

[0070] Example 2

[0071] The non-aqueous electrolyte for lithium-ion batteries was prepared using the same method as in Example 1, except that the electrolyte additive was replaced with the A23 compound provided in this invention.

[0072] Example 3

[0073] The non-aqueous electrolyte for lithium-ion batteries was prepared using the same method as in Example 1, except that the electrolyte additive was replaced with the A27 compound provided by this invention.

[0074] Example 4

[0075] The non-aqueous electrolyte for lithium-ion batteries was prepared using the same method as in Example 1, except that the electrolyte additive was replaced with the A28 compound provided in this invention.

[0076] Comparative Example 1

[0077] The non-aqueous electrolyte for lithium-ion batteries was prepared using the same method as in Example 1, except that no electrolyte additives were added.

[0078] Comparative Example 2

[0079] A non-aqueous electrolyte for lithium-ion batteries was prepared using the same method as in Example 1, except that the electrolyte additive was replaced with compound BO1, the structure of which is as follows:

[0080]

[0081] Comparative Example 3

[0082] The non-aqueous electrolyte for lithium-ion batteries was prepared using the same method as in Example 1, except that the electrolyte additive was replaced with compound BO2, the structure of which is as follows:

[0083]

[0084] The non-aqueous electrolytes for lithium-ion batteries obtained in Examples 2 to 4 and Comparative Examples 1 to 3 were all tested for performance using the same method as in Example 1. The specific data are shown in Table 1.

[0085] Table 1 Performance test data of lithium-ion batteries with non-aqueous electrolyte

[0086]

[0087] As can be seen from the data in Table 1, the nitrogen-containing heterocyclic difluorophosphate provided by this invention, based on the electron-rich nature of nitrogen atoms, can effectively neutralize free HF in the electrolyte, thereby inhibiting the decomposition of lithium hexafluorophosphate and thus improving the thermal stability and storage stability of lithium hexafluorophosphate.

[0088] III. Preparation of Lithium-ion Batteries

[0089] Application Example 1

[0090] (1) Preparation of positive electrode:

[0091] The battery positive electrode material (LiCoO2), conductive carbon black (particle size 1000nm) and PVDF (polyvinylidene fluoride) were weighed in a mass ratio of 90:5:5 and stirred in a magnetic stirrer for 2 hours to obtain a uniform slurry. Then, it was cut into circular positive electrode sheets with a diameter of 16mm. The positive electrode sheets were dried in a vacuum (200Pa) at 120℃ for 12 hours and then placed in a glove box for later use.

[0092] (2) Preparation of negative electrode sheet:

[0093] MCMB (mesophase carbon microspheres), acetylene black, thickener sodium carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber were mixed in a weight ratio of MCMB:acetylene black:styrene-butadiene rubber:CMC = 95:2:2:1. Then, deionized water was added, and the mixture was stirred in a vacuum mixer to obtain a negative electrode slurry. The negative electrode slurry was uniformly coated onto copper foil. After the copper foil was dried at room temperature, it was transferred to a 120°C oven to dry for 12 hours. Then, it was cold-pressed and slit to obtain a negative electrode sheet.

[0094] (3) Electrolyte preparation:

[0095] In a nitrogen-atmospheric glove box with a water content of <1ppm, ethylene carbonate, ethyl methyl carbonate, and propyl propionate organic solvents are mixed in a specific ratio. LiPF6 is dissolved in the organic solvents. Then, the lithium-ion battery non-aqueous electrolyte additive provided by this invention and other additives are added to the organic solvents, completely dissolved, and mixed evenly to obtain the electrolyte. EC has a low freezing point and needs to be preheated to 50°C on an electric magnetic stirrer. The LiPF6 content is 13.5wt%, and the weight ratio of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and propyl propionate (PP) is EC:EMC:PP = 30:50:20. The content of the novel lithium-ion battery electrolyte additive provided by this invention is 1wt% of the total weight of the electrolyte. The specific electrolyte formulation is shown in Table 2.

[0096] (4) Preparation of lithium-ion batteries:

[0097] A CR2430 coin cell was assembled using LiCoO2 material and MCMB as the working electrode, and a Celgard 2400 membrane (Tianjin) as the separator. The assembly sequence, from negative to positive, was as follows: negative electrode shell, spring, gasket, negative electrode sheet, electrolyte, separator, positive electrode sheet, and positive electrode shell, followed by sealing with a sealing machine. All operations were performed in a pure argon glove box. After standing for 6 hours, the cells were removed for electrochemical performance testing.

[0098] The electrolyte formulations in Application Examples 1-7 and Comparative Application Example 1-3 are shown in Table 2 below:

[0099] Table 2 shows the electrolyte formulations in Application Examples 1-7 and Comparative Application Example 1-3.

[0100]

[0101]

[0102] IV. Test

[0103] Performance tests were conducted on the lithium-ion batteries obtained from corresponding use cases 1 to 7 and comparative application examples 1 to 3.

[0104] Test 1: High and Low Temperature Performance Test of Lithium-ion Batteries

[0105] The prepared batteries were subjected to the following tests:

[0106] (1) High temperature cycle performance: The lithium-ion battery was placed in a constant temperature chamber at 45°C and charged to 4.2V with a constant current and constant voltage of 1C. Then it was discharged to 3.0V with a constant current of 1C and cycled for 100 cycles. The capacity retention rate of the lithium-ion battery was measured.

[0107] (2) High temperature storage performance: The formed lithium-ion battery was charged to 4.2V at room temperature with a constant current and constant voltage of 1C, and the initial capacity and internal resistance of the battery were measured. Then, after being stored in an environment of 60℃ for 15 days, it was discharged to 3V at 1C and then charged to 4.2V. The capacity and internal resistance of the lithium-ion battery were measured.

[0108] (3) Low temperature discharge performance: The formed lithium-ion battery was charged to 4.2V at room temperature using IC constant current and constant voltage, and the initial capacity of the battery was measured; then the battery was placed in a constant temperature chamber at -20℃ for 4.0 hours, and discharged to 2.5V at 0.5C, and the capacity of the lithium-ion battery was measured. Capacity retention rate = capacity after low temperature discharge / initial capacity.

[0109] Battery internal resistance change rate = battery internal resistance stored at 60℃ for 15 days / initial battery internal resistance.

[0110] In Table 3, batteries 1 to 7 correspond to the lithium-ion batteries prepared in Application Examples 1 to 7 above, and batteries 1# to 3# correspond to the lithium-ion batteries prepared in Comparative Application Examples 1 to 3 above.

[0111] Table 3 Capacity retention of lithium-ion batteries

[0112]

[0113]

[0114] As can be seen from Table 3 above, at 45℃, the lithium-ion battery made with the additive provided by this invention has significantly better high-temperature cycle performance, high-temperature storage performance, and low-temperature discharge performance in the range of 2.5 to 4.2V than battery #1 without the additive of this invention. Even batteries #2 and #3, which use the mainstream TFP as the additive, show obvious advantages in high-temperature cycle performance, high-temperature storage performance, and low-temperature discharge performance. This indicates that the additive described in this invention can improve the high-temperature and low-temperature performance of lithium-ion batteries, and in particular, can reduce battery impedance.

[0115] Test 2: Self-extinguishing time of lithium-ion battery electrolyte

[0116] The prepared lithium-ion battery electrolyte was subjected to a self-extinguishing time test. The test material was prepared from glass wool into spheres with a radius of 5 mm. The mass of each sphere was weighed and recorded. Then, the spheres were immersed in the electrolyte and weighed again. The difference in mass before and after immersion represents the mass of electrolyte absorbed by the glass wool sphere. Next, the sphere was placed on a circular iron wire and ignited using a gas ignition device. The time taken for the sphere to extinguish was recorded. The results are shown in Table 4. In Table 4, batteries 1 to 7 correspond to the lithium-ion batteries prepared in Application Examples 1 to 7, and batteries 1# to 3# correspond to the lithium-ion batteries prepared in Comparative Application Examples 1 to 3.

[0117] Table 4 Self-extinguishing time of electrolyte in lithium-ion batteries

[0118]

[0119]

[0120] As can be seen from Table 4, battery 1# without the additives described in this invention completely burned. The comparison between batteries 1-7 and batteries 2# and 3# shows that the lithium-ion battery electrolyte made with the additives provided in this invention has a significant flame-retardant effect.

[0121] A comparison of batteries 1-4 and battery 2# shows that, for lithium-ion batteries with the same amount of additives, batteries 1-4, which contain the additives described in this invention, have a better flame retardant effect than battery 1#, which uses TFP as the mainstream additive in the market.

[0122] Table 4 shows that the lithium-ion battery electrolyte with the additives described in this invention has good flame retardant effect, improves the safety of the electrolyte, and thus enhances the safety performance of the lithium-ion battery.

[0123] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are exhaustively listed. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0124] For those skilled in the art, various modifications and improvements can be made without departing from the concept of the present invention, and these modifications and improvements are all within the scope of protection of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A lithium-ion battery electrolyte additive, characterized in that, The additive is selected from any one or a mixture of the following structures:

2. A non-aqueous electrolyte for lithium-ion batteries, characterized in that, The electrolyte comprises a solvent, an electrolyte lithium salt, and additives, wherein the additives are one or a combination of several of the lithium-ion battery electrolyte additives described in claim 1.

3. The non-aqueous electrolyte for lithium-ion batteries according to claim 2, characterized in that, Based on the total mass of the electrolyte, the mass content of the additive is 0.01wt% to 10wt%.

4. The non-aqueous electrolyte for lithium-ion batteries according to claim 2, characterized in that, The electrolyte also includes auxiliary additives, which are one or a combination of 1,3-propanesulfonyl lactone, 1,4-butanesulfonyl lactone, propenyl-1,3-sulfonyl lactone, vinyl sulfate, methylene disulfonate, vinylene carbonate, fluoroethylene carbonate, lithium difluorosulfonylimide, lithium difluorooxalate borate, lithium difluorobis(oxalate) phosphate, lithium difluorophosphate, and lithium tetrafluoroborate. Based on the total mass of the electrolyte, the mass content of the auxiliary additive is 0.1 wt% to 3.0 wt%.

5. The non-aqueous electrolyte for lithium-ion batteries according to claim 2, characterized in that, The electrolyte lithium salt is one or a combination of several of LiPF6, LiClO4, LiBF4, LiBOB, LiODFB, LiTDI, LiTFSI and LiFSI.

6. The non-aqueous electrolyte for lithium-ion batteries according to claim 2, characterized in that, Based on the total mass of the electrolyte, the content of the lithium salt in the electrolyte is 10wt% to 20wt%.

7. The non-aqueous electrolyte for lithium-ion batteries according to claim 2, characterized in that, The solvent is one or a combination of several of the following: ethylene carbonate, propylene carbonate, γ-butyrolactone, phenyl acetate, 1,4-butylsulfonyl lactone, 3,3,3-trifluoropropylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, ethyl acetate, methyl propyl carbonate, propyl propionate, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 2,2-difluoroethyl acetate, 2,2-difluoroethyl propionate, and 2,2-difluoroethyl methyl carbonate.

8. A lithium-ion battery, characterized in that, The lithium-ion battery includes a negative electrode, a positive electrode, a separator disposed between the negative electrode and the positive electrode, and a non-aqueous electrolyte for lithium-ion batteries as described in any one of claims 2 to 7.

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