Ternary lithium ion battery electrolyte and ternary lithium ion battery thereof

Abstract

The invention discloses a ternary lithium ion battery electrolyte and a ternary lithium ion battery thereof. The ternary lithium ion battery electrolyte comprises a lithium salt, a non-aqueous organic solvent and an additive, the additive comprises a sulfonamide pyridinium onium salt compound shown in a structural formula I and an ethylene sulfate compound shown in a structural formula II, R1-R6 are independently selected from hydrogen, halogen, cyano, C1-C6 alkyl or C1-C6 alkyl substituted aryl, and R1-R6 are independently selected from hydrogen, halogen, cyano, C1-C6 alkyl or C1-C6 alkyl substituted aryl. R7 to R8 are independently selected from hydrogen and C1-C6 alkyl groups, or * represents a connecting end, or R7 and R8 are combined with each other to form a C3-C8 cyclic structure. The additive of the ternary lithium ion battery electrolyte comprises the sulfonamide pyridinium onium salt compound and the ethylene sulfate compound, and through the synergistic effect of the sulfonamide pyridinium onium salt compound and the ethylene sulfate compound, the high-temperature circulation and high-temperature storage performance of a ternary lithium ion battery can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a ternary lithium ion battery electrolyte and a ternary lithium ion battery thereof. Background Art

[0002] In recent years, lithium-ion batteries have been widely used in electric vehicles, hybrid vehicles, energy storage systems and portable electronic devices. With the advancement of technology, people's requirements for the performance of lithium-ion batteries are also constantly increasing.

[0003] Ternary lithium-ion batteries have a high energy density, and the compaction density of the electrode of the ternary battery can reach 3.3~3.5g / cm 3 , much higher than the 2.3~2.4g / cm of lithium iron phosphate 3 This results in a higher volumetric energy-to-energy ratio for ternary materials and batteries, enabling them to store more energy within a smaller volume and weight, thereby improving battery life and meeting the demand for long-range battery life in new energy vehicles and other devices. However, in high-temperature environments, the positive electrode material of ternary lithium-ion batteries easily decomposes, releasing oxygen molecules. These oxygen molecules react violently with the electrolyte, causing electrolyte combustion and, in turn, deflagration, posing a significant safety hazard. Therefore, higher requirements are placed on the high-temperature cycling and storage performance of ternary lithium-ion batteries. Summary of the Invention

[0004] During the research and development process, the applicant of the present invention discovered that the use of a sulfonamide pyridinium salt compound as an additive in a ternary lithium-ion battery can improve the battery's high-temperature performance to a certain extent. However, the compound's limited solubility and dispersibility in the electrolyte restricts its application in batteries. In view of the above-mentioned problems discovered during the research and development process, the present invention aims to provide a ternary lithium-ion battery electrolyte and a ternary lithium-ion battery thereof. The additives of the ternary lithium-ion battery electrolyte include a sulfonamide pyridinium salt compound and a vinyl sulfate compound. The combination of the two compounds can effectively improve the high-temperature cycling and high-temperature storage performance of the ternary lithium-ion battery.

[0005] To achieve the above objectives, the present invention provides a ternary lithium-ion battery electrolyte, comprising a lithium salt, a non-aqueous organic solvent, and an additive, wherein the additive comprises a sulfonamide pyridinium salt compound represented by structural formula I and a vinyl sulfate compound represented by structural formula II.

[0006] Structural Formula I Structural Formula II wherein R1 to R6 are each independently selected from hydrogen, halogen, cyano, C1 to C6 alkyl or aromatic group substituted by C1 to C6 alkyl, and R7 to R8 are each independently selected from hydrogen, C1 to C6 alkyl, or , * represents the connecting end, or R7 and R8 are combined with each other to form a ring structure of C3~C8.

[0007] Compared with the prior art, the additives of the ternary lithium-ion battery electrolyte of the present invention include sulfonamide pyridinium salt compounds and vinyl sulfate compounds, wherein the sulfur-containing groups of the sulfonamide pyridinium salt compounds can react with the electrode surface and form a stable interface film, thereby effectively avoiding the decomposition of the electrolyte and improving the high-temperature cycle performance. The nitrogen-containing groups also participate in the film formation process. The nitrogen atoms can combine with the active sites on the electrode surface to further enhance the stability of the interface film, thereby improving the high-temperature storage performance. At the same time, the sulfonimide anion group can promote the dissociation and transmission of lithium ions, thereby improving the charge and discharge efficiency of the battery. Generally, in the electrolyte, lithium salts such as LiPF6 will dissociate into Li + and PF6 - , and the sulfonimide anion may act as an additive or substitute anion to change the solvation structure of the electrolyte, thereby promoting the Li + However, the solubility of sulfonamide pyridinium salt compounds in electrolytes is limited, making it difficult to form a uniform and complete interfacial film, resulting in limited improvements in high-temperature cycling and storage performance. To this end, the present invention further introduces vinyl sulfate compounds. The sulfonic acid groups contained in these compounds combine with multiple oxygen atoms to form a dense SEI film, which can synergistically regulate the composition of the interfacial film, improve the uniformity and integrity of the interfacial film, and further enhance the stability of the non-aqueous electrolyte at high temperatures. Furthermore, the sulfate groups contained in these compounds are highly polar groups and can form good interactions with polar solvents (such as carbonates) in the electrolyte, thereby improving the dispersibility of the sulfonamide pyridinium salt compound and the vinyl sulfate compound in the electrolyte. This allows the sulfonamide pyridinium salt compound to be more uniformly adsorbed on the electrode surface, expanding the film-forming range. Therefore, the present invention, through the combined use of sulfonamide pyridinium salt compounds and vinyl sulfate compounds, can effectively improve the solubility and dispersibility of the sulfonamide pyridinium salt compound in the electrolyte, jointly construct a uniform and stable interfacial film, and effectively enhance the high-temperature storage and high-temperature cycling performance of ternary lithium-ion batteries.

[0008] Furthermore, R1 is selected from halogen or tolyl, R2 to R6 are each independently selected from hydrogen, halogen, cyano, C1 to C6 alkyl, R7 to R8 are each independently selected from hydrogen, C1 to C3 alkyl, or , * represents a connecting end, or R7 and R8 are combined with each other to form a C3~C6 cycloalkane.

[0009] Furthermore, the sulfonamide pyridinium salt compound includes at least one of Compound 1 to Compound 6,

[0010] Compound 1 Compound 2 Compound 3

[0011] Compound 4 Compound 5 Compound 6

[0012] Furthermore, the vinyl sulfate compound includes at least one of Compound 7 to Compound 10,

[0013] Compound 7 Compound 8 Compound 9 Compound 10.

[0014] Furthermore, the mass percentage of the sulfonamide pyridinium salt compound in the non-aqueous electrolyte is 0.01% to 0.5%.

[0015] Furthermore, the mass percentage of the vinyl sulfate compound in the non-aqueous electrolyte is 0.01% to 5%.

[0016] Furthermore, the lithium salt includes at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl imide), lithium bis(oxalatoborate), lithium difluorophosphate, lithium fluorosulfonate, lithium difluorooxalatoborate, lithium lower aliphatic carboxylate, lithium difluorobis(oxalatophosphate) and lithium bis(fluorosulfonyl imide).

[0017] Furthermore, the non-aqueous organic solvent includes at least one of γ-butyrolactone, γ-valerolactone, δ-valerolactone, methyl acetate, ethyl acetate, ethyl propionate, butyl acetate, propyl propionate, butyl propionate, ethylene carbonate, propylene carbonate, butylene carbonate, pentylene carbonate, vinylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl n-propyl carbonate, ethyl n-propyl carbonate, propylene carbonate, 1,3-dioxolane, 1,4-dioxolane, crown ether, tetrahydrofuran, 2-methyltetrahydrofuran, 2-trifluoromethyltetrahydrofuran, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether.

[0018] Further, the ternary lithium-ion battery electrolyte further includes an auxiliary agent, and the auxiliary agent includes at least one of fluoroethylene carbonate, vinylene carbonate, 1,3-propane sultone, ethylene sulfate, 1,3-propylene glycol cyclic sulfate, 1,4-butane sultone, triallyl phosphate, and succinic anhydride.

[0019] On the other hand, the present invention provides a ternary lithium-ion battery, including a positive electrode material, a negative electrode material, and the foregoing ternary lithium-ion battery electrolyte.

[0020] Further, the positive electrode material is selected from at least one of nickel cobalt manganese oxide and nickel cobalt aluminum oxide. Detailed Embodiments

[0021] The present invention provides a ternary lithium-ion battery, including a positive electrode material, a negative electrode material, and a ternary lithium-ion battery electrolyte. Among them, the ternary lithium-ion battery further includes a positive electrode material. The positive electrode material is selected from at least one of nickel cobalt manganese oxide and nickel cobalt aluminum oxide. Specifically, the chemical formula of nickel cobalt manganese oxide is LiNi x Co y Mn z M (1-x-y-z) O2, and the chemical formula of nickel cobalt aluminum oxide is LiNi x Co y Al z N (1-x-y-z) O2, where M is at least one of Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, and Ti, N is at least one of Mn, Mg, Cu, Zn, Sn, B, Ga, Cr, Sr, V, and Ti, 0 < x < 1, 0 < y < 1, 0 < z < 1, and x + y + z ≤ 1. The negative electrode material is selected from at least one of artificial graphite, natural graphite, lithium titanate, silicon-carbon composite material, and silicon monoxide. As an example, the negative electrode material is artificial graphite, but it is not limited thereto.

[0022] The ternary lithium-ion battery electrolyte of the present invention includes a lithium salt, a non-aqueous organic solvent, an additive, and an auxiliary agent. The additive includes a sulfonamidopyridinium salt compound shown in Structural Formula I and a vinyl sulfate compound shown in Structural Formula II.

[0023] Structural Formula I Structural Formula II Among them, R1 to R6 are each independently selected from hydrogen, halogen, cyano, C1 to C6 alkyl, or an aromatic group substituted by C1 to C6 alkyl, and R7 to R8 are each independently selected from hydrogen, C1 to C6 alkyl, or , * represents a connecting end, or R7 and R8 are combined to form a C3~C8 ring structure. Further, R1 is selected from halogen or tolyl, R2~R6 are independently selected from hydrogen, halogen, cyano, C1~C6 alkyl, R7~R8 are independently selected from hydrogen, C1~C3 alkyl, or , * represents a connecting end, or R7 and R8 are combined to form a C3~C6 cycloalkane. Further, R1 is selected from fluorine or tolyl, R2~R6 are independently selected from hydrogen, fluorine, cyano, methyl, R7~R8 are independently selected from hydrogen, methyl, or And R7 and R8 are not at the same time or , * represents a connecting end, or R7 and R8 are combined with each other to form cyclohexane.

[0024] The sulfonamide pyridinium salt compound includes at least one of Compound 1 to Compound 6, but is not limited thereto. The mass percentage of the sulfonamide pyridinium salt compound in the non-aqueous electrolyte is 0.01% to 0.5%. Preferably, the mass percentage of the sulfonamide pyridinium salt compound in the non-aqueous electrolyte is 0.05% to 0.4%. More preferably, the mass percentage of the sulfonamide pyridinium salt compound in the non-aqueous electrolyte is 0.01% to 0.2%. By way of example, the mass percentage of the sulfonamide pyridinium salt compound in the non-aqueous electrolyte may be, but is not limited to, 0.01%, 0.02%, 0.04%, 0.06%, 0.08%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%.

[0025]

[0026] Compound 1 Compound 2 Compound 3

[0027] Compound 4 Compound 5 Compound 6

[0028] Specifically, compound 1 can be prepared according to the following synthetic route:

[0029]

[0030] The specific preparation method can be: (1) Preparation of fluorosulfonic acid isocyanate: 68 g of anhydrous potassium fluoride was placed in a multi-necked flask equipped with a speed-regulating stirrer, a condensing reflux tube, and a constant-pressure dropping funnel. The stirrer was turned on for stirring. The multi-necked flask was then placed in a water bath. The temperature of the water bath was controlled at 100° C. The temperature of the cold water in the condensing reflux tube was controlled at −20° C. 141.5 g of chlorosulfonic acid isocyanate was slowly added dropwise to the multi-necked flask using a constant-pressure dropping funnel. After the addition was complete, the temperature of the water bath was controlled at 130° C. The mixture was refluxed for 6 h. After the reaction was completed, atmospheric distillation was performed at 100° C. The fractions in the temperature range of 65–100° C. were collected to obtain 106 g of fluorosulfonic acid isocyanate with a yield of 85% and a purity of 99%.

[0031] (II) Preparation of compound 1 (1) 16 g of 2-methylpyridine and 80 g of toluene were stirred at 0°C for 10 min to form a first solution; (2) The second solution was added dropwise to the first solution and reacted for 2.5 hours. The second solution was formed by uniformly mixing 21.5 g of fluorosulfonic acid isocyanate and 80 g of toluene. (3) The product after the reaction in step (2) was filtered, washed with toluene, and dried in vacuo at 100°C for 15 h to obtain 36.0 g of compound 1 with a yield of 96% and a purity of 99%.

[0032] The synthetic routes and specific preparation methods of compounds 3, 4, and 5 can refer to compound 1, except that 2-methylpyridine (CAS: 109-06-8) is replaced by 2-fluoropyridine (CAS: 372-48-5), pyridine (CAS: 110-86-1), and 2-cyanopyridine (CAS: 1945-84-2), respectively.

[0033] Compound 2 can be prepared according to the following synthetic route:

[0034] Compound 6 can be prepared according to the following synthetic route:

[0035] The vinyl sulfate compound includes at least one of Compound 7 to Compound 10, but is not limited thereto. The mass percentage of the vinyl sulfate compound in the non-aqueous electrolyte is 0.01% to 5%. Preferably, the mass percentage of the vinyl sulfate compound in the non-aqueous electrolyte is 0.05% to 4%. More preferably, the mass percentage of the vinyl sulfate compound in the non-aqueous electrolyte is 0.1% to 2%. As an example, the mass percentage of the vinyl sulfate compound in the non-aqueous electrolyte can be, but is not limited to, 0.01%, 0.02%, 0.04%, 0.06%, 0.08%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, and 5%.

[0036]

[0037] Compound 7 Compound 8 Compound 9 Compound 10.

[0038] Among them, the CAS number of compound 7 is 2507955-35-1; the CAS number of compound 8 is 14131298-10-0; the CAS number of compound 9 is 124535-97-3; and the CAS number of compound 10 is 6970-90-7.

[0039] The lithium salt of the present invention includes at least one of lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(trifluoromethanesulfonyl imide) (LiN(CF3SO2)2), lithium bis(oxalatoborate) (C4BLiO8), lithium difluorophosphate (LiPO2F2), lithium fluorosulfonate (LiSO2F), lithium difluorooxalatoborate (LiODFB), lithium lower aliphatic carboxylate, lithium difluorobis(oxalatophosphate) (LiDODFP) and lithium bis(fluorosulfonyl imide) (LiFSI). As an example, the lithium salt is lithium hexafluorophosphate (LiPF6), but is not limited thereto. Furthermore, the lithium salt is a mixture of lithium hexafluorophosphate (LiPF6) and lithium bis(oxalatoborate) (C4BLiO8), but is not limited thereto. The mass percentage of the lithium salt in the non-aqueous electrolyte of the present invention is 5% to 25%. Further, the mass percentage of the lithium salt in the non-aqueous electrolyte is 8% to 20%. More preferably, the mass percentage of the lithium salt in the non-aqueous electrolyte is 10% to 15%. For example, the mass percentage of the lithium salt in the non-aqueous electrolyte may be, but is not limited to, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, and 25%.

[0040] The non-aqueous organic solvents of the present invention include γ-butyrolactone (γ-Bt), γ-valerolactone (GVL), δ-valerolactone (DVL), methyl acetate (MA), ethyl acetate (EA), ethyl propionate (EP), butyl acetate (n-Ba), propyl propionate (n-PP), butyl propionate (PRB), ethylene carbonate (EC), propylene carbonate (PCA), butylene carbonate (BC), pentylene carbonate, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl n-propyl carbonate, At least one of ethyl n-propyl carbonate, propylene carbonate (PC), 1,3-dioxolane (DOL), 1,4-dioxolane (DX), crown ether, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-CH3-THF), 2-trifluoromethyltetrahydrofuran (2-CF3-THF), dimethoxymethane (DMM), diethoxymethane (DEM), ethoxymethoxymethane (DCE), ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether (EDB), and diethylene glycol dimethyl ether (DEGME). The mass percentage of the non-aqueous solvent in the non-aqueous electrolyte of the present invention is 65-90%. Preferably, the mass percentage of the non-aqueous organic solvent in the non-aqueous electrolyte is 75-89%. More preferably, the mass percentage of the non-aqueous organic solvent in the non-aqueous electrolyte is 78-88%. For example, the mass percentage of the non-aqueous organic solvent in the non-aqueous electrolyte may be, but is not limited to, 65%, 70%, 75%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, or 90%.

[0041] The ternary lithium-ion battery electrolyte of the present invention further includes an auxiliary agent, which includes at least one of fluoroethylene carbonate (FEC), vinylene carbonate (VC), 1,3-propane sultone (PS), diethylene sulfate (DTD), 1,3-propylene glycol cyclic sulfate (PCS), 1,4-butane sultone (1,4-BS), triallyl phosphate (TAP), and succinic anhydride (SA). The mass percentage of the auxiliary agent of the present invention in the non-aqueous electrolyte is 0.1-5%. As an example, the mass percentage of the auxiliary agent in the non-aqueous electrolyte can be, but is not limited to, 0.1%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, and 5.0%.

[0042] In order to better illustrate the purpose, technical solutions and beneficial effects of the present invention, the present invention will be further described below in conjunction with specific embodiments. It should be noted that the following implementation method is a further explanation of the present invention and should not be used as a limitation of the present invention.

[0043] Where specific conditions are not specified in the examples, conventional conditions or those recommended by the manufacturer may be used. Reagents or instruments used without manufacturer's indication are all commercially available conventional products.

[0044] Example 1 (1) Preparation of non-aqueous electrolyte Under an argon atmosphere and in a vacuum glove box with a moisture content of <1ppm, ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a weight ratio of EC:EMC=3:7. Then, various additives were added, dissolved, and thoroughly stirred, and LiPF6 was added. After mixing evenly, a non-aqueous electrolyte was obtained.

[0045] (2) Preparation of positive electrode Nickel cobalt manganese oxide material LiNi 0.6 Co 0.2 Mn 0.2 O2, adhesive PVDF and conductive agent SuperP are evenly mixed in a mass ratio of 95:1:4 to prepare a lithium secondary battery positive electrode slurry with a certain viscosity. The mixed slurry is coated on both sides of an aluminum foil, dried and rolled to obtain a positive electrode sheet.

[0046] (3) Preparation of negative electrode The negative electrode graphite material, adhesive PVDF and conductive agent SuperP are evenly mixed in a mass ratio of 90:2:8 to prepare a lithium secondary battery negative electrode slurry with a certain viscosity. The mixed slurry is coated on both sides of the copper foil, dried and rolled to obtain the negative electrode sheet.

[0047] (4) Preparation of lithium-ion batteries The positive electrode sheet, separator, and negative electrode sheet are stacked in order and then stacked as needed. After the tabs are welded, they are placed in the aluminum-plastic film of the battery packaging. The prepared non-aqueous electrolyte is injected into the dried bare cell. The cells are then vacuum packaged, allowed to stand, formed (charged at a constant current of 0.05C to 3.0V, then at a constant current of 0.1C to 3.3V), shaped, and tested for capacity. Finally, a 1Ah soft-pack lithium secondary battery is obtained.

[0048] The non-aqueous electrolyte formulations of Examples 2 to 22 and Comparative Examples 1 to 6 are shown in Table 1. The steps for preparing the electrolytes and manufacturing the batteries are the same as those of Example 1.

[0049] Table 1 Formula of non-aqueous electrolyte of Examples and Comparative Examples

[0050] The lithium-ion batteries prepared in Examples 1 to 22 and Comparative Examples 1 to 6 were subjected to high-temperature storage tests and high-temperature cycle tests, respectively. The specific test conditions are as follows. The performance test results are shown in Table 2.

[0051] High temperature storage performance test At room temperature (25°C), the lithium-ion battery is charged and discharged at 0.3C / 0.3C (the battery discharge capacity is recorded as C0), with an upper limit voltage of 4.45V; the battery is placed in a 60°C oven for 30 days, the battery is taken out, and the battery is placed in a 25°C environment and discharged at 0.3C, with the discharge capacity recorded as C1; then the lithium-ion battery is charged and discharged at 0.3C / 0.3C (the battery discharge capacity is recorded as C2), and the capacity retention rate and capacity recovery rate of the lithium-ion battery are calculated using the following formula: Capacity retention rate = C1 / C0×100% Capacity recovery rate = C2 / C0×100% High temperature cycle performance test Place the lithium-ion battery in a 45°C constant temperature box and let it stand for 30 minutes to allow the lithium-ion battery to reach a constant temperature. Then charge it at a constant current of 4C to a voltage of 4.45V, then charge it at a constant voltage of 4.45V to a current of 0.05C. Then discharge it at a constant current of 4C to a voltage of 2.5V. Record the first discharge capacity of the battery as C0. This is one charge and discharge cycle. Then, charge and discharge it at 1C / 1C for 1000 cycles at 45°C. Record the discharge capacity as C1. Use the following formula to calculate the capacity retention rate of the lithium-ion battery.

[0052] Capacity retention rate = C1 / C0×100% Coulombic efficiency of charge and discharge At room temperature (25°C), a lithium-ion battery is subjected to a 0.5C / 0.5C cycle with an upper voltage of 4.45V, a lower voltage of 3V, and a cutoff current of 0.05C. The charge capacity is recorded as C0 and the discharge capacity is recorded as C1. Calculate the coulombic efficiency using the following formula: Coulombic efficiency = (C1 / C0) × 100% Table 2 Performance test results of ternary lithium-ion batteries of the embodiment and comparative example

[0053] As shown in Table 2, the non-aqueous electrolyte of the present invention can effectively improve the high-temperature storage and high-temperature cycling performance of the ternary lithium-ion battery by using the sulfonamide pyridinium salt compound represented by structural formula I and the vinyl sulfate compound represented by structural formula II.

[0054] Further, from Examples 1 to 8 and Examples 15 to 19, it can be seen that when the sulfonamide pyridinium salt compound is Compound 1 and the vinyl sulfate compound is Compound 7, it has even better high-temperature storage and high-temperature cycling performance. This may be because the structure of Compound 1 contains fluorine and sulfur-containing groups, which can react with the electrode surface to form a stable passivation film, thereby preventing further decomposition of the electrolyte and improving high-temperature cycling performance. Nitrogen-containing groups also participate in the film formation process. Nitrogen atoms can bind to active sites on the electrode surface to further enhance the stability of the interfacial film, thereby improving high-temperature storage performance. At the same time, the sulfonimide anion group can promote the dissociation and transport of lithium ions, thereby improving the charge and discharge efficiency of the battery. At the same time, because of the fluorine and sulfur-containing groups in the structure, it is more stable than other components in the electrolyte at high voltage, thereby protecting the stability of the electrolyte. Compound 7 contains both sulfate and ester groups. The sulfate groups combine with multiple oxygen atoms to form a dense SEI film, which improves the thermal stability of the electrolyte and prevents gas generation from decomposition at high temperatures. Sulfate groups are highly polar groups and interact well with polar solvents (such as carbonates) in the electrolyte, thereby improving the additive's dispersibility. The ring structure also helps resist chemical and electrochemical degradation in the electrolyte, extending the additive's service life. The ester groups can solvate with lithium salts in the electrolyte. The oxygen atoms in the ester groups can form coordination bonds with lithium ions, helping to stabilize the lithium ions in the electrolyte. This solvation enhances the electrolyte's ionic conductivity, further improving the battery's high-temperature storage and cycling performance. Furthermore, the ester groups stabilize the electrode-electrolyte interface. They bind to active sites on the electrode surface, preventing the decomposition of organic solvents in the electrolyte at high voltages and maintaining the stability of the electrode-electrolyte interface. Therefore, combining these two compounds effectively improves high-temperature cycling and storage performance.

[0055] A comparison of Examples 1-5 and Examples 15-19 shows that further adding an additive to the electrolyte can further improve the high-temperature storage and high-temperature cycling performance. Further, Examples 19-22 show that when DTD is used as the additive, the performance is even better. This may be because the combination of the sulfonamide pyridinium salt compound and the vinyl sulfate compound itself improves the high-temperature cycling and high-temperature storage performance. After the addition of DTD, it preferentially decomposes at high temperatures to form sulfur-containing compounds (such as Li2S and Li2SO4). These products can form a dense CEI film on the positive electrode surface, effectively preventing electrolyte oxidation and transition metal dissolution, and improving high-temperature stability. At the same time, DTD can still stably form a film in the high voltage range, inhibiting the oxidative decomposition of the electrolyte, and improving the cycle performance of the battery at high temperatures.

[0056] As shown in Examples 1 and 9-10, with increasing mass of Compound 1, both high-temperature cycling performance and high-temperature storage performance showed an increasing trend. Furthermore, as shown in Comparative Examples 2 and 4-6, in the absence of vinyl sulfate compounds, with increasing mass of sulfonamide pyridinium salt compounds, high-temperature cycling performance and high-temperature storage performance did not improve and even showed a decreasing trend. This suggests that the introduction of vinyl sulfate compounds of the present invention may effectively improve the solubility and dispersibility of sulfonamide pyridinium salt compounds in the electrolyte, thereby improving the high-temperature storage and high-temperature cycling performance of ternary lithium-ion batteries.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the scope of protection of the present invention. Although the present invention is described in detail with reference to the preferred embodiments, it is not limited to those listed in the embodiments. Those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A ternary lithium-ion battery electrolyte comprising a lithium salt, a non-aqueous organic solvent, and an additive, characterized in that: The additives include a sulfonamide pyridinium salt compound shown in structural formula I and a vinyl sulfate compound shown in structural formula II. Structural Formula I Structural Formula II wherein R1 to R6 are each independently selected from hydrogen, halogen, cyano, C1 to C6 alkyl or aromatic group substituted by C1 to C6 alkyl, and R7 to R8 are each independently selected from hydrogen, C1 to C6 alkyl, or , * represents the connecting end, or R7 and R8 are combined with each other to form a ring structure of C3~C8.

2. The ternary lithium-ion battery electrolyte according to claim 1, wherein R1 is selected from halogen or tolyl, R2 to R6 are each independently selected from hydrogen, halogen, cyano, C1 to C6 alkyl, R7 to R8 are each independently selected from hydrogen, C1 to C3 alkyl, or , * represents a connecting end, or R7 and R8 are combined with each other to form a C3~C6 cycloalkane.

3. The ternary lithium-ion battery electrolyte according to claim 1 or 2, characterized in that The sulfonamide pyridinium salt compound includes at least one of Compound 1 to Compound 6, Compound 1 Compound 2 Compound 3 Compound 4 Compound 5 Compound 6 4. The ternary lithium-ion battery electrolyte according to claim 1 or 2, wherein: The vinyl sulfate compound includes at least one of Compound 7 to Compound 10, Compound 7 Compound 8 Compound 9 Compound 10.

5. The ternary lithium-ion battery electrolyte according to claim 1 or 2, characterized in that: The mass percentage of the sulfonamide pyridinium salt compound in the non-aqueous electrolyte is 0.01% to 0.5%, and the mass percentage of the vinyl sulfate compound in the non-aqueous electrolyte is 0.01% to 5%.

6. The ternary lithium-ion battery electrolyte according to claim 1 or 2, characterized in that: The lithium salt includes at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, lithium bistrifluoromethanesulfonyl imide, lithium bisoxalatoborate, lithium difluorophosphate, lithium fluorosulfonate, lithium difluorooxalatoborate, lithium lower aliphatic carboxylate, lithium difluorobisoxalatophosphate and lithium bisfluorosulfonyl imide.

7. The ternary lithium-ion battery electrolyte according to claim 1 or 2, characterized in that: The non-aqueous organic solvent includes at least one of γ-butyrolactone, γ-valerolactone, δ-valerolactone, methyl acetate, ethyl acetate, ethyl propionate, butyl acetate, propyl propionate, butyl propionate, ethylene carbonate, propylene carbonate, butylene carbonate, pentylene carbonate, vinylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl n-propyl carbonate, ethyl n-propyl carbonate, propylene carbonate, 1,3-dioxolane, 1,4-dioxolane, crown ether, tetrahydrofuran, 2-methyltetrahydrofuran, 2-trifluoromethyltetrahydrofuran, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether.

8. The ternary lithium-ion battery electrolyte according to claim 1 or 2, characterized in that: The invention also includes an auxiliary agent, which includes at least one of fluoroethylene carbonate, vinylene carbonate, 1,3-propane sultone, vinyl sulfate, 1,3-propylene glycol cyclic sulfate, 1,4-butane sultone, triallyl phosphate, and succinic anhydride.

9. A ternary lithium-ion battery, characterized in that: The invention comprises a positive electrode material, a negative electrode material and a ternary lithium-ion battery electrolyte as claimed in any one of claims 1 to 7.

10. The ternary lithium-ion battery according to claim 8, wherein: The positive electrode material is selected from at least one of nickel-cobalt-manganese oxide and nickel-cobalt-aluminum oxide.

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