A ternary lithium ion battery electrolyte and application thereof

Abstract

The application discloses a ternary lithium ion battery electrolyte and application and belongs to the field of lithium ion batteries. The electrolyte is added with saturated asymmetric cyclic sulfide, saturated symmetric cyclic sulfide and fluorine-containing ester compound or fluorine-containing ether compound additive, which synergistically forms an SEI film composed of organic sulfide and inorganic matter at the negative electrode. The SEI film has the characteristics of fast Li+ conduction speed and compactness and is not easy to dissolve. The electrolyte has the dual advantages of good low-temperature discharge performance and excellent high-temperature storage performance when used in the ternary lithium ion battery.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion batteries, and specifically relates to a ternary lithium-ion battery electrolyte and its application. Background Technology

[0002] Energy is the material foundation for human survival and economic development. Building a safe, efficient, clean, economical, and stable energy system is crucial for sustainable social development. The development of new energy vehicles can effectively address the challenges of the energy crisis and environmental pollution, achieving sustainable development of the automotive industry, and enabling leapfrog development of China's automotive industry. Pure electric vehicles and hybrid electric vehicles are important directions for the future development of the automotive industry, and power batteries are the key core technology for new energy vehicles. As the industrialization of electric vehicles deepens, governments and enterprises worldwide are increasing their efforts to develop the power battery industry. When applied to power batteries, compared with lead-acid, nickel-cadmium, and nickel-metal hydride batteries, lithium-ion batteries have advantages such as high energy density, long cycle life, good consistency, and good safety. Considering overall performance, cost, and industrial maturity, lithium-ion power batteries are currently the optimal choice for new energy vehicles and have become the most widely used power batteries in new energy vehicles. Compared with lithium cobalt oxide, lithium iron phosphate, and lithium manganese oxide batteries, ternary batteries have high energy density (single cell energy density of 150–200 Wh·kg). -1 High-nickel ternary lithium batteries can achieve an energy density of 300Wh·kg. -1 The above features include a high voltage plateau (3.6–3.7V) and high tap density (the tap density of ternary materials is approximately 2.0–2.4 g·cm³). -3 Ternary lithium batteries possess characteristics such as good cycle performance (1500-2000 cycles) and electrochemical stability, giving them a significant advantage in improving the driving range of new energy vehicles. However, they suffer from poor high-temperature storage performance and mediocre low-temperature performance. Therefore, comprehensively improving the wide-temperature range performance of ternary lithium batteries is crucial for promoting their application in the new energy vehicle field.

[0003] Electrolytes determine the high and low temperature performance, high rate capability, cycle life, and safety performance of batteries, and are a key factor restricting the development of wide-temperature-range lithium-ion batteries. When the operating temperature is too low, the conductivity of the electrolyte decreases significantly, Li+ solvation is enhanced, SEI film impedance increases, and solvent and lithium salts precipitate. At higher temperatures, various complex side reactions occur within the electrolyte itself and between the electrodes and the electrolyte. Improving the high and low temperature performance of ternary batteries by adjusting the electrolyte formulation is a more effective method. However, current research on improving the temperature characteristics of lithium-ion batteries mostly focuses on either low-temperature or high-temperature performance. While some progress has been made in both areas, these research results cannot simply be combined to further broaden the operating temperature range of lithium batteries. Developed low-temperature lithium batteries generally have poor high-temperature performance, while high-temperature lithium batteries often have poor low-temperature performance. Developing electrolytes that simultaneously address both high and low temperature performance is crucial for breaking through the limitations of wide-temperature-range lithium-ion battery technology. Summary of the Invention

[0004] The purpose of this invention is to provide an electrolyte that improves the high and low temperature performance of ternary lithium-ion batteries. This electrolyte contains saturated asymmetric cyclic sulfides, and the saturated symmetric cyclic sulfides, along with fluorinated ester or fluorinated ether additives, synergistically form an SEI film at the negative electrode composed of organic sulfides and inorganic substances. This film also possesses the ability to conduct Li... + It exhibits characteristics of high speed and dense, non-dissolving properties. When used in ternary lithium-ion batteries, this electrolyte offers the dual advantages of excellent low-temperature discharge performance and superior high-temperature storage performance.

[0005] To achieve the above objectives, the specific solution adopted by the present invention is as follows:

[0006] A ternary lithium-ion battery electrolyte comprises the following components:

[0007] 1) One or more lithium salts;

[0008] 2) One or more ester solvents:

[0009] 3) A saturated asymmetric cyclic sulfide additive:

[0010] The saturated asymmetric cyclic sulfide additive includes one or more of the following: 1,3-propanesulfonate lactone, 4-methyl ethylene sulfate, 4-propyl ethylene sulfate, 4-ethyl ethylene sulfate, butyl sulfonate lactone, and butylene sulfite.

[0011] 4) A saturated symmetrical cyclic sulfide additive:

[0012] The saturated symmetrical cyclic sulfide additive includes one or more of the following: methylene disulfonate, sulfolane, propylene sulfate, vinyl sulfate, and propylene sulfite.

[0013] The mass ratio of the saturated asymmetric cyclic sulfide additive to the saturated symmetric cyclic sulfide additive is 1:0.5-1.5, preferably 1:1-1.2;

[0014] 5) A fluorinated ester compound or fluorinated ether compound additive.

[0015] Further, the lithium salt includes one or more of the following: LiPF6 (lithium hexafluorophosphate), LiBF4 (lithium tetrafluoroborate), LiClO4 (lithium perchlorate), LiAsF6 (lithium hexafluoroarsenate), LiBOB (lithium bis(oxalato)borate), LiODFB (lithium difluorooxalato)borate, LiFSI (lithium bis(fluorosulfonyl)imide), and LiTFSI (lithium bis(trifluoromethanesulfonyl)imide). LiPF6 is preferred.

[0016] Furthermore, the lithium salt concentration in the ester solvent is 0.8 mol / L to 3 mol / L, preferably 1 to 2 mol / L.

[0017] Further, the fluorinated ester or fluorinated ether additive includes one or more of the following: fluoroethylene carbonate, trifluoropropylene carbonate, methyl difluoroacetate, ethyl difluoroacetate, perfluorobutyl methyl ether, and ethyl perfluorobutyl ether. The mass concentration of the fluorinated ester or fluorinated ether additive is 0.1% to 10% of the total mass of the lithium salt and ester solvent, preferably 0.2% to 5%, and more preferably 1% to 3%.

[0018] Further, the ester solvent includes one or more of the following: ethylene carbonate, propylene carbonate, diethyl carbonate, methyl ethyl carbonate, dimethyl carbonate, methyl acetate, ethyl acetate, n-butyl acetate, and isobutyl acetate.

[0019] The preferred materials are a mixture of ethylene carbonate, diethyl carbonate, and methyl ethyl carbonate.

[0020] Furthermore, the mass concentration of the saturated asymmetric cyclic sulfide additive is 0.3% to 5% of the total mass of lithium salt and ester solvent, preferably 0.5% to 2%;

[0021] Furthermore, the mass concentration of the saturated symmetrical cyclic sulfide additive is 0.05% to 7.5% of the total mass of lithium salt and ester solvent, preferably 0.2% to 3%.

[0022] Furthermore, the electrolyte also contains other additives, including one or more of vinylene carbonate, ethylene ethylene carbonate, lithium difluorophosphate, and tripropynyl phosphate. The mass concentration of the other additives is 0.1% to 5% of the total mass of the lithium salt and ester solvent, preferably 0.5% to 3%.

[0023] An application of the above-mentioned electrolyte in ternary lithium-ion batteries.

[0024] Furthermore, the operating temperature of ternary lithium-ion batteries is -40℃ to 55℃.

[0025] The beneficial effects of this invention are:

[0026] This electrolyte has a high decomposition temperature resistance, resulting in a denser SEI film on the electrode surface. This SEI film exhibits excellent high-temperature resistance, is not easily decomposed or dissolved, and thus can suppress side reactions at the electrode / electrolyte interface in ternary lithium-ion batteries under high temperature and high pressure, reduce reversible / irreversible Li+ consumption, and improve interface stability. Furthermore, this SEI film possesses high Li+ content. + The increased transport rate reduces the impedance of the SEI film, significantly improving the battery's low-temperature discharge performance. Ternary lithium-ion batteries exhibit excellent high-temperature storage performance and low-temperature discharge performance in the improved electrolyte. Detailed Implementation

[0027] The following non-limiting embodiments are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the invention in any way.

[0028] Example 1

[0029] Electrolyte: The lithium salt is LiPF6 (lithium hexafluorophosphate), with a concentration of 1.0 mol / L. The solvent is a mixture of ethylene carbonate, diethyl carbonate, and methyl ethyl carbonate in a volume ratio of 1:1:8. Additives include 1,3-propanesulfonate lactone, vinyl sulfate, vinylene carbonate, fluoroethylene carbonate, and lithium difluorophosphate. The mass fractions are 0.5%, 0.5%, 0.5%, 2%, and 1.5% of the total mass of lithium salt and solvent, respectively.

[0030] The positive electrode of a ternary lithium-ion battery is prepared as follows: LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 The mass ratio of O2, conductive carbon black, and PVDF (polyvinylidene fluoride) is 94:4:2 (positive electrode active material). This mixture is dissolved in N-methylpyrrolidone, thoroughly mixed, and then coated onto both sides of aluminum foil. The solid-liquid ratio is 1:2, and the positive electrode active material loading is 5 mg / cm³. 2After vacuum drying, the material is cut into rectangular electrode sheets with a length of 200 mm and a width of 146 mm using a slicer. The negative electrode of the battery is prepared as follows: graphite, hard carbon, conductive carbon black, and PVDF binder are mixed in a mass ratio of 60:30:8:2 (negative electrode active material) with an appropriate amount of water. The mixture is then coated on both sides of copper foil with a solid-liquid ratio of 1:1.5 and a negative electrode active material loading of 2.8 mg / cm³. 2 After vacuum drying, the electrodes are cut into rectangular electrode sheets with a length of 200 mm and a width of 146 mm using a slicer. Using SC12 as the separator, multiple soft-pack batteries are assembled in a drying room, with 25 g of electrolyte added. The assembled batteries are then subjected to high-temperature formation, high-temperature aging, room-temperature aging, and secondary capacity testing to form a complete SEI film on the electrode surface.

[0031] Battery high-temperature storage performance test method:

[0032] 1. Under ambient temperature of 25℃±2℃, charge at 1C constant current and constant voltage to 4.2V, with a cutoff current of 0.05C;

[0033] 2. Let stand for 1 hour at an ambient temperature of 25℃±2℃;

[0034] 3. Under ambient temperature of 25℃±2℃, discharge at a constant current of 1C to 2.8V (record the discharge capacity C1);

[0035] 4. Let stand for 1 hour at an ambient temperature of 25℃±2℃;

[0036] 5. Under ambient temperature of 25℃±2℃, charge at 1C constant current and constant voltage to 4.2V, with a cutoff current of 0.05C;

[0037] 6. Let stand for 7 days at an ambient temperature of 55℃±2℃;

[0038] 7. Let stand for 24 hours at an ambient temperature of 25℃±2℃;

[0039] 8. Under ambient temperature of 25℃±2℃, discharge at a constant current of 1C to 2.8V (record the discharge capacity C2);

[0040] 9. Let stand for 1 hour at an ambient temperature of 25℃±2℃;

[0041] 10. Under ambient temperature of 25℃±2℃, charge at 1C constant current and constant voltage to 4.2V, with a cutoff current of 0.05C;

[0042] 11. Let stand for 1 hour at an ambient temperature of 25℃±2℃;

[0043] 12. Under ambient temperature of 25℃±2℃, discharge at a constant current of 1C to 2.8V (record the discharge capacity C3);

[0044] Remaining capacity calculation method: (C2 / C1)*100%; Restored capacity calculation method: (C3 / C1)*100%.

[0045] Battery low-temperature discharge performance test method:

[0046] 1. Under ambient temperature of 25℃±2℃, charge at 1C constant current and constant voltage to 4.2V, with a cutoff current of 0.05C;

[0047] 2. Let stand for 1 hour at an ambient temperature of 25℃±2℃;

[0048] 3. Under an ambient temperature of 25℃±2℃, discharge at a constant current of 1C for 42 minutes, i.e., adjust to 30% SOC;

[0049] 4. Let stand at -30℃±2℃ for 24 hours;

[0050] 5. Discharge with at least 35A current for 2 seconds.

[0051] The test results are shown in Table 1.

[0052] Example 2

[0053] Electrolyte: The lithium salt is LiPF6, with a concentration of 1.0 mol / L. The solvent is a mixture of ethylene carbonate, diethyl carbonate, and methyl ethyl carbonate in a volume ratio of 1:1:8. Additives include 1,3-propanesulfonyl lactone, methylene disulfonate, vinylene carbonate, fluoroethylene carbonate, and lithium difluorophosphate. The mass fractions are 0.5%, 0.5%, 0.5%, 2%, and 1.5% of the total mass of the lithium salt and ester solvent, respectively.

[0054] The testing method is the same as in Example 1;

[0055] The test results are shown in Table 1.

[0056] Example 3

[0057] Electrolyte: The lithium salt used in the electrolyte is LiPF6, with a concentration of 1.0 mol / L. The solvent is a mixture of ethylene carbonate, diethyl carbonate, and methyl ethyl carbonate in a volume ratio of 1:1:8. Additives include 4-propyl ethylene sulfate, ethylene sulfate, ethylene carbonate, fluoroethylene carbonate, and lithium difluorophosphate. The mass fractions are 0.5%, 0.5%, 0.5%, 2%, and 1.5% of the total mass of the lithium salt and ester solvent, respectively.

[0058] The testing method is the same as in Example 1;

[0059] The test results are shown in Table 1.

[0060] Example 4

[0061] Electrolyte: The lithium salt is LiPF6, with a concentration of 1.0 mol / L. The solvent is a mixture of ethylene carbonate, diethyl carbonate, and methyl ethyl carbonate in a volume ratio of 1:1:8. Additives include 1,3-propanesulfonate lactone, vinyl sulfate, vinylene carbonate, propylene trifluorocarbonate, and lithium difluorophosphate. The mass fractions are 0.5%, 0.5%, 0.5%, 2%, and 1.5% of the total mass of the lithium salt and ester solvent, respectively.

[0062] The testing method is the same as in Example 1;

[0063] The test results are shown in Table 1.

[0064] Example 5

[0065] Electrolyte: The lithium salt is LiPF6, with a concentration of 1.0 mol / L. The solvent is a mixture of ethylene carbonate, diethyl carbonate, and methyl ethyl carbonate in a volume ratio of 1:1:8. Additives include 1,3-propanesulfonate lactone, vinyl sulfate, vinylene carbonate, fluoroethylene carbonate, and lithium difluorophosphate. The mass fractions are 1%, 1%, 0.5%, 2%, and 1.5% of the total mass of the lithium salt and ester solvent, respectively.

[0066] The testing method is the same as in Example 1;

[0067] The test results are shown in Table 1.

[0068] Example 6

[0069] Electrolyte: The lithium salt used in the electrolyte is LiPF6, with a concentration of 1.0 mol / L. The solvent is a mixture of ethylene carbonate, diethyl carbonate, and methyl ethyl carbonate in a volume ratio of 1:1:8. Additives include 1,3-propanesulfonate lactone, vinyl sulfate, vinylene carbonate, fluoroethylene carbonate, and lithium difluorophosphate. The mass fractions are 0.5%, 0.3%, 0.5%, 2%, and 1.5% of the total mass of the lithium salt and ester solvent, respectively.

[0070] The testing method is the same as in Example 1;

[0071] The test results are shown in Table 1.

[0072] Comparative Example 1

[0073] The high-temperature electrolyte was purchased from Guangzhou Tinci, model number TC-EFF05;

[0074] The positive electrode of a ternary lithium-ion battery is prepared as follows: LiNi 1 / 3 Co 1 / 3 Mn 1 / 3O2, conductive carbon black, and binder are dissolved in an appropriate amount of N-methylpyrrolidone at a mass ratio of 94:4:2, mixed evenly, and then coated on both sides of aluminum foil. The positive electrode active material loading is 5 mg / cm³. 2 After vacuum drying, the material is cut into rectangular electrode sheets with a length of 200 mm and a width of 146 mm using a slicer for later use. The negative electrode of the battery is prepared as follows: graphite, hard carbon, conductive carbon black, and binder are dissolved in an appropriate amount of water in a mass ratio of 60:30:8:2, mixed evenly, and then coated on both sides of copper foil. The active material loading of the negative electrode is 2.8 mg / cm³. 2 After vacuum drying, the electrodes are cut into rectangular electrode sheets with a length of 200 mm and a width of 146 mm using a slicer. Using Celgard 2500 as the separator, multiple soft-pack batteries are assembled in a drying room, with 25 g of electrolyte added. The assembled batteries are then subjected to high-temperature formation, high-temperature aging, room-temperature aging, and secondary capacity testing to form a complete SEI film on the electrode surface.

[0075] Battery high-temperature storage performance test method:

[0076] 1. Under ambient temperature of 25℃±2℃, charge at 1C constant current and constant voltage to 4.2V, with a cutoff current of 0.05C;

[0077] 2. Let stand for 1 hour at an ambient temperature of 25℃±2℃;

[0078] 3. Under ambient temperature of 25℃±2℃, discharge at a constant current of 1C to 2.8V (record the discharge capacity C1);

[0079] 4. Let stand for 1 hour at an ambient temperature of 25℃±2℃;

[0080] 5. Under ambient temperature of 25℃±2℃, charge at 1C constant current and constant voltage to 4.2V, with a cutoff current of 0.05C;

[0081] 6. Let stand for 7 days at an ambient temperature of 55℃±2℃;

[0082] 7. Let stand for 24 hours at an ambient temperature of 25℃±2℃;

[0083] 8. Under ambient temperature of 25℃±2℃, discharge at a constant current of 1C to 2.8V (record the discharge capacity C2);

[0084] 9. Let stand for 1 hour at an ambient temperature of 25℃±2℃;

[0085] 10. Under ambient temperature of 25℃±2℃, charge at 1C constant current and constant voltage to 4.2V, with a cutoff current of 0.05C;

[0086] 11. Let stand for 1 hour at an ambient temperature of 25℃±2℃;

[0087] 12. Under ambient temperature of 25℃±2℃, discharge at a constant current of 1C to 2.8V (record the discharge capacity C3);

[0088] Remaining capacity calculation method: (C2 / C1)*100%; Restored capacity calculation method: (C3 / C1)*100%.

[0089] Battery low-temperature discharge performance test method:

[0090] 1. Under ambient temperature of 25℃±2℃, charge at 1C constant current and constant voltage to 4.2V, with a cutoff current of 0.05C;

[0091] 2. Let stand for 1 hour at an ambient temperature of 25℃±2℃;

[0092] 3. Under an ambient temperature of 25℃±2℃, discharge at a constant current of 1C for 42 minutes, i.e., adjust to 30% SOC;

[0093] 4. Let stand at -30℃±2℃ for 24 hours;

[0094] 5. Discharge with at least 35A current for 2 seconds.

[0095] The test results are shown in Table 1.

[0096] Comparative Example 2 (without symmetrical cyclic sulfides)

[0097] Electrolyte: The lithium salt used in the electrolyte is LiPF6, with a concentration of 1.0 mol / L. The solvent is a mixture of ethylene carbonate, diethyl carbonate, and methyl ethyl carbonate in a volume ratio of 1:1:8. The additives are 1,3-propanesulfonyl lactone, vinylene carbonate, fluoroethylene carbonate, and lithium difluorophosphate, with mass fractions of 0.5%, 0.5%, 2%, and 1.5% of the total mass of the lithium salt and ester solvent, respectively.

[0098] The testing method is the same as that of Comparative Example 1;

[0099] The test results are shown in Table 1.

[0100] Comparative Example 3 (without asymmetry)

[0101] Electrolyte: The lithium salt is LiPF6, with a concentration of 1.0 mol / L. The solvent is a mixture of ethylene carbonate, diethyl carbonate, and methyl ethyl carbonate in a volume ratio of 1:1:8. Additives include ethylene sulfate, vinylene carbonate, fluoroethylene carbonate, and lithium difluorophosphate. The mass fractions are 0.5%, 0.5%, 2%, and 1.5% of the total mass of the lithium salt and ester solvent, respectively.

[0102] The testing method is the same as that of Comparative Example 1;

[0103] The test results are shown in Table 1.

[0104] Comparative Example 4 (Asymmetric: Symmetrical Proportion Control)

[0105] Electrolyte: The lithium salt used is LiPF6, with a concentration of 1.0 mol / L. The solvent is a mixture of ethylene carbonate, diethyl carbonate, and methyl ethyl carbonate in a volume ratio of 1:1:8. Additives include 1,3-propanesulfonate lactone, vinyl sulfate, vinylene carbonate, fluoroethylene carbonate, and lithium difluorophosphate. The mass fractions are 0.5%, 1%, 0.5%, 2%, and 1.5% of the total mass of the lithium salt and ester solvent, respectively.

[0106] The testing method is the same as that of Comparative Example 1;

[0107] The test results are shown in Table 1.

[0108] Comparative Example 5

[0109] Electrolyte: The lithium salt is LiPF6, with a concentration of 1.0 mol / L. The solvent is a mixture of ethylene carbonate, diethyl carbonate, and methyl ethyl carbonate in a volume ratio of 1:1:8. Additives include 1,3-propanesulfonate lactone, vinyl sulfate, vinylene carbonate, fluoroethylene carbonate, and lithium difluorophosphate. The mass fractions are 0.2%, 0.2%, 0.5%, 2%, and 1.5% of the total mass of the lithium salt and ester solvent, respectively.

[0110] The testing method is the same as that of Comparative Example 1;

[0111] The test results are shown in Table 1.

[0112] Comparative Example 6

[0113] Electrolyte: The lithium salt is LiPF6, with a concentration of 1.0 mol / L. The solvent is a mixture of ethylene carbonate, diethyl carbonate, and methyl ethyl carbonate in a volume ratio of 1:1:8. Additives include 1,3-propanesulfonate lactone, vinyl sulfate, vinylene carbonate, fluoroethylene carbonate, and lithium difluorophosphate. The mass fractions are 6%, 6%, 0.5%, 2%, and 1.5% of the total mass of the lithium salt and ester solvent, respectively.

[0114] The testing method is the same as that of Comparative Example 1;

[0115] The test results are shown in Table 1.

[0116] Comparative Example 7 (linear sulfides)

[0117] Electrolyte: The lithium salt is LiPF6, with a concentration of 1.0 mol / L. The solvent is a mixture of ethylene carbonate, diethyl carbonate, and methyl ethyl carbonate in a volume ratio of 1:1:8. Additives include 1,3-propanesulfonate lactone, dimethyl sulfite, vinylene carbonate, fluoroethylene carbonate, and lithium difluorophosphate. The mass fractions are 0.5%, 0.5%, 0.5%, 2%, and 1.5% of the total mass of the lithium salt and ester solvent, respectively.

[0118] The testing method is the same as that of Comparative Example 1;

[0119] The test results are shown in Table 1. Table 1: Examples 1-6 and Comparative Examples 1-7 show the discharge capacity, capacity retention rate and recovery rate of the ternary lithium-ion batteries before and after being stored at a high temperature of 55°C, as well as the cutoff voltage of the batteries at the end of 2s of discharge at -30°C.

[0120] Comparative Example 8 (without fluorinated esters or fluorinated ethers as additives)

[0121] Electrolyte: The lithium salt is LiPF6 (lithium hexafluorophosphate), with a concentration of 1.0 mol / L. The solvent is a mixture of ethylene carbonate, diethyl carbonate, and methyl ethyl carbonate in a volume ratio of 1:1:8. The additives are 1,3-propanesulfonate lactone, vinyl sulfate, vinylene carbonate, and lithium difluorophosphate. The mass fractions are 0.5%, 0.5%, 0.5%, and 1.5% of the total mass of lithium salt and solvent, respectively.

[0122] The testing method is the same as that of Comparative Example 1;

[0123] The test results are shown in Table 1.

[0124] Table 1

[0125]

[0126] As can be seen from the above examples, comparative experimental data, and battery performance results, ternary lithium-ion batteries, by optimizing the electrolyte composition and simultaneously adding saturated asymmetric cyclic sulfides, saturated symmetrical cyclic sulfides, and fluorinated ester or fluorinated ether compounds as additives, and further controlling the ratio between each component (the mass ratio of saturated asymmetric cyclic sulfide additives to saturated symmetrical cyclic sulfide additives is 1:0.5-1.5), exhibit a synergistic effect among the various electrolyte components, promoting the formation of a highly stable SEI film composed of organic sulfides and inorganic substances at the negative electrode. This film also possesses the ability to conduct Li-... +The SEI film exhibits high speed and is dense and difficult to dissolve. It demonstrates excellent high-temperature resistance, is not easily decomposed or dissolved, thus suppressing side reactions at the electrode / electrolyte interface in ternary lithium-ion batteries under high temperature and high pressure, reducing reversible / irreversible Li+ consumption, and improving interface stability. Furthermore, the SEI film possesses a high Li+ transport rate, resulting in reduced SEI film impedance and improved low-temperature discharge performance. Ternary lithium-ion batteries, in the improved electrolyte, exhibit excellent high-temperature storage performance and low-temperature discharge performance, significantly enhancing the wide-temperature range performance of ternary lithium-ion batteries.

Claims

1. A ternary lithium-ion battery electrolyte, characterized in that: The electrolyte comprises the following components: 1) one or more lithium salts; 2) one or more ester solvents; 3) a saturated asymmetric cyclic sulfide additive; The saturated non-symmetrical cyclic sulfide additive includes one or more of: 1,3 Propane sulfone, 4 Methyl ethyl sulfide, 4 Propyl ethyl sulfide, 4 Ethyl ethyl sulfide, butyl sulfone, butylene sulfite; 4) a saturated symmetric cyclic sulfide additive; The saturated symmetric cyclic sulfide additive comprises one or more of the following: methylene dithiocarbonate, sulfolane, propylene sulfate, ethylene sulfate, propylene sulfite; The mass ratio of the saturated asymmetric cyclic sulfide additive to the saturated symmetric cyclic sulfide additive is: 1:0.5 1.5; 5) a fluorine-containing ester compound or a fluorine-containing ether compound additive.

2. The electrolyte according to claim 1, wherein: The lithium salt comprises one or more of the following: lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisoxalate borate, lithium difluorooxalate borate, lithium bisfluorosulfonimide, lithium bis-trifluoromethanesulfonimide; The concentration of the lithium salt in the ester solvent is 0.8-3 mol / L.

3. The electrolyte according to claim 1, wherein: The fluorine-containing ester compound or fluorine-containing ether compound additive comprises one or more of the following: fluoroethylene carbonate, trifluoropropylene carbonate, difluoromethyl acetate, difluoroethyl acetate, perfluorobutyl methyl ether, ethyl perfluorobutyl ether; The mass concentration of the fluorine-containing ester compound or fluorine-containing ether compound additive is 0.1-10% of the total mass of the lithium salt and the ester solvent.

4. The electrolyte according to claim 1, wherein: The ester solvent comprises one or more of the following: ethylene carbonate, propylene carbonate, diethyl carbonate, methyl ethyl carbonate, dimethyl carbonate, methyl acetate, ethyl acetate, n-butyl acetate, isobutyl acetate.

5. The electrolyte according to claim 1, wherein: The mass concentration of the saturated asymmetric cyclic sulfide additive is 0.3-5% of the total mass of the lithium salt and the ester solvent; The mass concentration of the saturated symmetric cyclic sulfide additive is 0.05-7.5% of the total mass of the lithium salt and the ester solvent.

6. The electrolyte according to claim 1, wherein: The electrolyte further comprises other additives, and the other additives comprise one or more of the following: vinylene carbonate, vinyl ethylene carbonate, lithium difluorophosphate, tripropargyl phosphate, and the mass concentration of the other additives is 0.1-5% of the total mass of the lithium salt and the ester solvent.

7. A method according to claim 1 6. Use of any of the electrolytes in a ternary lithium-ion battery.

8. Use according to claim 7, characterized in that: The application temperature of the ternary lithium-ion battery is 40°C to 55°C.

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