An aromatic asymmetric lithium salt, a lithium battery electrolyte and a lithium battery

Abstract

The application provides a kind of aromatic asymmetric lithium salt, lithium battery electrolyte and lithium battery, the aromatic asymmetric lithium salt has the structure general formula shown in formula I.The aromatic asymmetric lithium salt provided by the application has higher dissociation constant, ionic conductivity and lithium ion transference number in carbonate-based and ether-based electrolyte.Due to the structural symmetry of the lithium salt anion, the corrosion of the lithium battery positive electrode current collector aluminum foil is greatly reduced, the solubility of the decomposition product formed in the electrolyte is reduced, the surface of the aluminum foil can be effectively passivated, the corrosion behavior of the sulfonimide organic lithium salt on the positive electrode current collector under high temperature and high pressure is inhibited, and the stable operation of the battery is ensured.

Description

Technical Field

[0001] This invention relates to the field of electrochemical energy storage technology, and in particular to an aromatic asymmetric lithium salt, a lithium battery electrolyte, and a lithium battery. Background Technology

[0002] In recent years, new energy technologies have flourished, and how to store and utilize these "green energies" with low loss has become crucial. Lithium-ion batteries, as a new type of electrochemical energy storage device, have become one of the research hotspots in the energy field over the past three decades. They are widely used in 3C products due to their advantages such as high voltage, high energy density, long cycle life, and no memory effect, and are gradually expanding into new directions such as new energy vehicles (electric vehicles, hybrid vehicles) and smart grids. This places more stringent requirements on the performance of lithium-ion batteries, especially in high-temperature and high-pressure operation and high-rate charge / discharge performance.

[0003] Currently, the operating temperature of lithium batteries based on commercial carbonate electrolytes is generally limited to below 50°C. This is because excessively high temperatures can lead to problems such as the decomposition of the lithium salt (lithium hexafluorophosphate, LiPF6), an increase in organic solvent side reactions, an increase in internal battery impedance, a decrease in voltage plateau, and rapid capacity decay. A key factor is the poor thermal stability and water sensitivity of the lithium hexafluorophosphate used, making it difficult to apply under harsh conditions such as high temperature and high pressure.

[0004] To address the aforementioned bottlenecks, sulfonylimide-based lithium salts (lithium bispentafluoroethylsulfonylimide LiBETI, lithium bistrifluoromethylsulfonylimide LiTFSI, and lithium bisfluorosulfonylimide LiFSI) have gradually gained attention from academia and industry. As a class of organic lithium salts, they exhibit high anionic charge delocalization, complete dissociation in organic solvents, high ionic conductivity, and stability to water and high temperatures, often used as additives in high-temperature safe electrolyte systems. Compared to lithium hexafluorophosphate, these organic lithium salts possess numerous advantages, but their large-scale application remains hindered by the corrosion problem of aluminum current collectors in lithium-ion battery cathodes. According to literature (Nat. Mater. 2022, 21, 455-462), carbonate electrolytes using lithium salt LiTFSI cause severe corrosion to the aluminum current collector at voltages above 3.8V, and high temperatures accelerate this process. This persistent corrosion behavior is closely related to the good solubility of its decomposition product Al(TFSI)3 in the electrolyte. Several methods exist to suppress the corrosion of aluminum current collectors by sulfonylimide lithium salts: increasing the lithium salt content to prepare high-concentration electrolytes (Nat. Energy 2019, 4, 269-280), adding boron-containing lithium salts to passivate the aluminum foil surface (Energy Storage Mater. 2019, 23, 646-652), or adding isocyanate additives to slow down the aluminum corrosion rate (CN116525948A). Most of these techniques have significant inhibitory effects, but as the positive electrode voltage increases, the number of cycles increases, and high-temperature operating conditions become increasingly demanding, their effectiveness often diminishes significantly. Furthermore, some methods are too costly and lack economic benefits, hindering large-scale implementation. Therefore, it is urgent to address this problem fundamentally, specifically by reforming the lithium salt structure. Summary of the Invention

[0005] This invention provides an aromatic asymmetric lithium salt, a lithium battery electrolyte, and a lithium battery to solve the problem of corrosion of current collector aluminum foil by sulfonylimide-based organic lithium salts in the prior art, and to achieve stable cycle performance of lithium batteries under high temperature and high pressure.

[0006] In a first aspect, the present invention provides an aromatic asymmetric lithium salt having the general structural formula shown in Formula I:

[0007]

[0008] Z1 and Z2 may be the same or different, and each is independently selected from one of sulfinyl group and sulfonyl group;

[0009] R1 is selected from one of the following: fluorine atom, chlorine atom, bromine atom, iodine atom, cyano, phenyl, halophenyl, trimethylsilyl, trifluoromethylsilyl, alkyl with 1 to 10 carbon atoms, and haloalkyl with 1 to 10 carbon atoms;

[0010] X1, X2, X3, X4, and X5 may be the same or different, and each is independently selected from one of the following: hydrogen atom, fluorine atom, chlorine atom, bromine atom, iodine atom, cyano group, phenyl group, halophenyl group, trimethylsilyl group, trifluoromethylsilyl group, alkyl group with 1 to 10 carbon atoms, and haloalkyl group with 1 to 10 carbon atoms.

[0011] The alkyl halogroup can be a monoalkyl halogroup or a polyalkyl halogroup, and a polyalkyl halogroup refers to a group having more than one halogen atom; the halogen in the alkyl halogroup can be fluorine, chlorine, bromine or iodine, preferably fluorine.

[0012] The halophenyl group can be a monohalophenyl or a polyhalophenyl group, where a polyhalophenyl group has more than one halogen atom. The halogen in the halophenyl group can be fluorine, chlorine, bromine or iodine, preferably fluorine.

[0013] Preferably, Z1 and Z2 may be the same or different, and each is independently selected from sulfinyl or sulfonyl groups; R1 is selected from atoms or functional groups with strong electron-withdrawing ability, such as fluorine atoms, cyano groups, and haloalkyl groups with 1 to 10 carbon atoms; X1, X2, X3, X4, and X5 may be the same or different, and each is independently selected from hydrogen atoms, halogen atoms, alkyl groups with 1 to 10 carbon atoms, and haloalkyl groups with 1 to 10 carbon atoms.

[0014] More preferably, Z1 and Z2 are both sulfonyl groups; R1 is selected from fluorine atoms and fluoroalkyl groups having 1 to 10 carbon atoms; X1, X2, X3, X4, and X5 may be the same or different, and each is independently selected from hydrogen atoms, fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms.

[0015] In some embodiments of the present invention, the aromatic asymmetric lithium salt is one of the following lithium salt compounds 1-8.

[0016]

[0017]

[0018] The aromatic asymmetric lithium salt of the present invention can be prepared by designing synthetic routes based on its structural formula through various basic reaction types known in the art, and the yields of various synthetic routes will vary.

[0019] In one embodiment of the present invention, the aromatic asymmetric lithium salt is lithium salt compound 1, and its preparation method includes:

[0020] The first step involves dissolving trifluoromethylsulfonamide in acetonitrile. After the sample is completely dissolved, potassium carbonate is added, and the mixture is stirred at room temperature. Pentafluorophenylsulfonyl chloride is separately dissolved in acetonitrile. Once a homogeneous solution is formed, it is slowly added dropwise to the first solution at low temperature. After the reaction, the resulting mixture is filtered, and the filtrate is rotary evaporated to obtain the potassium salt intermediate. The second step involves dissolving the intermediate in acetonitrile and adding lithium perchlorate to perform a displacement reaction to obtain the target product. The synthetic route is shown below:

[0021]

[0022] In another embodiment of the present invention, the aromatic asymmetric lithium salt is lithium salt compound 2, and its preparation method includes:

[0023] The first step involves dissolving trifluoromethanesulfonamide in acetonitrile. After complete dissolution, potassium carbonate is added, and the mixture is stirred at room temperature. Trifluoro(meta-para-meta)phenylsulfonyl chloride is separately dissolved in acetonitrile. After a homogeneous phase is formed, it is slowly added dropwise to the above solution at low temperature. After the reaction, the resulting mixture is filtered, and the filtrate is rotary evaporated to obtain the potassium salt intermediate. The second step involves dissolving the intermediate in acetonitrile and adding lithium perchlorate to perform a substitution reaction to obtain the target product. The synthetic route is shown below:

[0024]

[0025] The synthetic route provided by this invention is relatively simple. Those skilled in the art can replace some of the raw materials accordingly to obtain aromatic asymmetric lithium salts with other structures.

[0026] In a second aspect, the present invention provides a lithium battery electrolyte comprising the above-mentioned aromatic asymmetric lithium salt.

[0027] The aromatic asymmetric lithium salt provided by this invention exhibits high dissociation constants, ionic conductivity, and lithium-ion transference numbers in carbonate-based and ether-based electrolytes. Because the lithium salt anion no longer possesses structural symmetry, its corrosiveness to the aluminum foil of the lithium battery cathode current collector is significantly reduced. The decomposition products formed have lower solubility in the electrolyte, effectively passivating the aluminum foil surface and inhibiting the corrosion behavior of the sulfonylimide-based organic lithium salt on the cathode current collector under high temperature and pressure, ensuring stable battery operation. Therefore, the aromatic asymmetric lithium salt of this invention can be applied to lithium battery electrolytes.

[0028] Specifically, the aromatic asymmetric lithium salt serves as a lithium salt electrolyte and / or additive. In other words, the aromatic asymmetric lithium salt can be used as a lithium salt electrolyte in a lithium battery electrolyte, or as an additive in a lithium battery electrolyte, or simultaneously as both a lithium salt electrolyte and an additive in a lithium battery electrolyte.

[0029] When the aromatic asymmetric lithium salt is used as a lithium salt electrolyte, or simultaneously as a lithium salt electrolyte and an additive, the amount of the aromatic asymmetric lithium salt is 0.01 to 80% based on the mass of the lithium battery electrolyte.

[0030] When the aromatic asymmetric lithium salt is used only as an additive, the amount of the aromatic asymmetric lithium salt is 0.01 to 50% based on the mass of the lithium battery electrolyte.

[0031] The lithium battery electrolyte of this invention further includes organic solvents, optional other lithium salt electrolytes, and optional other additives. That is, the use of aromatic asymmetric lithium salts as lithium salt electrolytes and / or additives does not preclude the inclusion of other components that can serve as lithium salt electrolytes and / or additives in the electrolyte.

[0032] Specifically, when the aromatic asymmetric lithium salt is used as the lithium salt electrolyte, the lithium battery electrolyte also includes organic solvents and other additives. In addition, other lithium salt electrolytes may be added as needed.

[0033] When the aromatic asymmetric lithium salt is used as an additive, the lithium battery electrolyte also includes organic solvents and other lithium salt electrolytes. In addition, other additives may be added as needed.

[0034] When the aromatic asymmetric lithium salt is used as both a lithium salt electrolyte and an additive, the lithium battery electrolyte also includes an organic solvent. In addition, other lithium salt electrolytes and other additives may be added as needed.

[0035] In the above technical solution, to ensure the effect of inhibiting aluminum foil corrosion, if other lithium salt electrolytes are added, the proportion of the aromatic asymmetric lithium salt in the total lithium salt electrolyte is preferably 10% or more. If other additives are added, the proportion of the aromatic asymmetric lithium salt in the total additives is preferably 10% or more.

[0036] In the above technical solution, the organic solvent is selected from one or more of ethylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, propylene carbonate, vinylene carbonate, fluoroethylene carbonate, diethyl ether, ethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, and methyltetrahydrofuran.

[0037] The present invention has found that the aromatic asymmetric lithium salt of the present invention has high dissociation constant, ionic conductivity and lithium ion transference number in conventional carbonate-based and ether-based electrolytes.

[0038] In some embodiments of the present invention, the other lithium salt electrolyte is selected from one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate, lithium trifluoromethanesulfonate, lithium perchlorate, lithium nitrate, lithium sulfate, lithium oxalate, lithium difluorooxalateborate, lithium tetrafluoroborate, and lithium bis(oxalateborate).

[0039] In some embodiments of the present invention, the other additives are selected from one or more of lithium nitrate, lithium perchlorate, lithium sulfate, lithium oxalate, lithium carbonate, lithium oxide, lithium halide, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate, lithium trifluoromethanesulfonate, lithium difluorooxalateborate, lithium tetrafluoroborate, and lithium bis(oxalateborate).

[0040] In one embodiment of the present invention, the aromatic asymmetric lithium salt is used as a lithium salt electrolyte, and the organic solvent is propylene carbonate.

[0041] In another embodiment of the present invention, the aromatic asymmetric lithium salt is used as a lithium salt electrolyte, and the organic solvent is ethylene carbonate and diethyl carbonate in a volume ratio of 1:1.

[0042] Thirdly, the present invention provides a lithium battery comprising any of the aforementioned lithium battery electrolytes. Specifically, the lithium battery provided by the present invention contains the aromatic asymmetric lithium salt described in the present invention in its electrolyte.

[0043] The lithium battery described in this invention is not limited in shape and can be cylindrical, aluminum-cased, plastic-cased, or pouch-cased.

[0044] Furthermore, the lithium battery also includes a positive electrode, a negative electrode, and a separator placed between the positive and negative electrodes.

[0045] The cathode can be lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese oxide, or a ternary cathode material, preferably a ternary cathode material. For example, LiNi x Co y Mn 1-x-y O2, where 0 < x < 1, 0 < y < 1, and x + y < 1.

[0046] The negative electrode is a lithium metal negative electrode, a graphite negative electrode, a silicon negative electrode, or a silicon-carbon composite negative electrode.

[0047] The diaphragm is a polyolefin diaphragm, a polyimide diaphragm, or an electrospun diaphragm. It is preferably a polypropylene or polyethylene film.

[0048] This invention provides an aromatic asymmetric lithium salt, a lithium battery electrolyte, and a lithium battery. The aromatic asymmetric lithium salt, obtained through structural design, retains a highly delocalized sulfonylimide structure. This lithium salt exhibits high dissociation constant, ionic conductivity, and lithium-ion transference number in the electrolyte. Because the symmetric structure of the lithium salt anion is disrupted, the solubility of its decomposition products from the reaction with aluminum foil is significantly reduced in the electrolyte. This effectively passivates the positive electrode aluminum foil current collector of the lithium battery, inhibits the corrosion behavior of the sulfonylimide-based organic lithium salt on the aluminum foil under high temperature and pressure, and ensures stable battery operation. Attached Figure Description

[0049] Figure 1 The chronoamperometry curve of aluminum foil in the electrolyte of Example 1 at a constant voltage of 4.3V for 10 hours;

[0050] Figure 2 The chronoamperometry curve of aluminum foil in the electrolyte of Example 4 at a constant voltage of 4.3V for 10 hours;

[0051] Figure 3 The chronoamperometry curve of aluminum foil in the electrolyte of Comparative Example 1 at a constant voltage of 4.3V for 10 hours is shown.

[0052] Figure 4 The graph shows the cycle performance of the NCM811 / Li battery in the electrolytes of Example 9 and Comparative Example 2. Detailed Implementation

[0053] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0054] Unless otherwise specified, the technical means used in the embodiments of the present invention are all conventional means well known to those skilled in the art.

[0055] The organic solvents, lithium salt electrolytes, and additives used in the embodiments and comparative examples of this invention are all battery grade. The aromatic asymmetric lithium salt prepared in this invention has undergone multiple purification steps, rigorous drying, and standardized characterization.

[0056] In the following examples, the electrolyte was prepared in a glove box filled with 99.999% pure argon gas, with a water and oxygen content of less than 0.01 ppm and a temperature of room temperature.

[0057] Synthesis example 1

[0058] Synthesize lithium salt compound 1, whose structural formula is as follows: Its synthetic route is as follows:

[0059]

[0060] The specific synthesis steps are as follows:

[0061] First, 2.59 g of trifluoromethylsulfonamide was dissolved in an appropriate amount of acetonitrile. After the sample was completely dissolved, 6.0 g of potassium carbonate was added, and the mixture was stirred at room temperature (25°C). Then, 5.0 g of pentafluorophenylsulfonyl chloride was separately dissolved in a small amount of acetonitrile. After a homogeneous solution was formed, the solution was slowly added dropwise to the above solution at low temperature. After reacting at room temperature (25°C) for 48 hours, the resulting mixture was filtered, and the filtrate was rotary evaporated to obtain the potassium salt intermediate.

[0062] In the second step, 6.0g of potassium salt intermediate product was dissolved in an appropriate amount of acetonitrile, and 1.6g of lithium perchlorate was added to carry out a displacement reaction to obtain the target product.

[0063] The characterization data of the target product are as follows: 19 FNMR (400MHz, DMSO): -78.07, -137.75, -149.63, -161.62.

[0064] Synthesis example 2

[0065] Synthesize lithium salt compound 2, whose structural formula is Its synthetic route is as follows:

[0066]

[0067] The specific synthesis steps are the same as in Synthesis Example 1, except that pentafluorophenylsulfonyl chloride is replaced with 3,4,5-trifluorophenylsulfonyl chloride.

[0068] The characterization data of the target product are as follows: 19 FNMR (400MHz, DMSO): -77.98, -132.76, -156.36.

[0069] Synthesis example 3

[0070] Synthesize lithium salt compound 3, whose structural formula is as follows: Its synthetic route is as follows:

[0071]

[0072] The specific synthesis steps are the same as in Synthesis Example 1, except that pentafluorophenylsulfonyl chloride is replaced with 2,4,6-trifluorophenylsulfonyl chloride.

[0073] The characterization data of the target product are as follows: 19 FNMR (400MHz, DMSO): -77.98, -103.11, -103.48.

[0074] Synthesis example 4

[0075] Synthesize lithium salt compound 4, whose structural formula is Its synthetic route is as follows:

[0076]

[0077] The specific synthesis steps are the same as in Synthesis Example 1, except that pentafluorophenylsulfonyl chloride is replaced with 3,5-difluorophenylsulfonyl chloride.

[0078] The characterization data of the target product are as follows: 19 FNMR (400MHz, DMSO): -77.99, -107.92.

[0079] Synthesis example 5

[0080] Synthesize lithium salt compound 5, whose structural formula is as follows: Its synthetic route is as follows:

[0081]

[0082] The specific synthesis steps are the same as in Synthesis Example 1, except that pentafluorophenylsulfonyl chloride is replaced with 4-fluorophenylsulfonyl chloride.

[0083] The characterization data of the target product are as follows: 19 FNMR (400MHz, DMSO): -77.98, -103.20.

[0084] Synthesis example 6

[0085] Synthesize lithium salt compound 6, whose structural formula is as follows: The specific synthesis steps are as follows: 3.5g of potassium fluoro(pentafluorobenzene)sulfonylimide was dissolved in an appropriate amount of acetonitrile, stirred at room temperature (25℃) to homogenize, and 1.06g of lithium perchlorate was added to carry out a displacement reaction to obtain the target product.

[0086] Synthesis Example 7

[0087] Synthesize lithium salt compound 7, whose structural formula is

[0088] The specific synthesis steps are the same as in Synthesis Example 6, except that the potassium fluoro(pentafluorobenzene)sulfonylimide salt is replaced with the potassium fluoro(3,4,5-fluorobenzene)sulfonylimide salt.

[0089] Synthesis example 8

[0090] Synthesize lithium salt compound 8, whose structural formula is

[0091] The specific synthesis steps are the same as in Synthesis Example 6, except that the potassium salt of fluoro(pentafluorobenzene)sulfonylimide is replaced with the potassium salt of fluoro(3,5-fluorobenzene)sulfonylimide.

[0092] Example 1

[0093] This embodiment provides a lithium battery electrolyte comprising the above-mentioned aromatic asymmetric lithium salt compound 1, which is prepared as follows:

[0094] In an argon-filled glove box, take 385g of the above lithium salt compound 1 and 1000mL of propylene carbonate, and dissolve and stir until a clear solution is obtained.

[0095] Example 2

[0096] This embodiment provides a lithium battery electrolyte comprising the above-mentioned aromatic asymmetric lithium salt compound 2, which is prepared as follows:

[0097] In an argon-filled glove box, 349g of the above lithium salt compound 2 and 1000mL of propylene carbonate were dissolved and stirred until a clear solution was obtained.

[0098] Example 3

[0099] This embodiment provides a lithium battery electrolyte comprising the above-mentioned aromatic asymmetric lithium salt compound 3, which is prepared as follows:

[0100] In an argon-filled glove box, 349g of the above lithium salt compound 3 and 1000mL of propylene carbonate were dissolved and stirred until a clear solution was obtained.

[0101] Example 4

[0102] This embodiment provides a lithium battery electrolyte comprising the above-mentioned aromatic asymmetric lithium salt compound 4, which is prepared as follows:

[0103] In an argon-filled glove box, 331g of the above lithium salt compound 4 and 1000mL of propylene carbonate were dissolved and stirred until a clear solution was obtained.

[0104] Example 5

[0105] This embodiment provides a lithium battery electrolyte comprising the above-mentioned aromatic asymmetric lithium salt compound 5, which is prepared as follows:

[0106] In an argon-filled glove box, 313g of the above lithium salt compound 5 and 1000mL of propylene carbonate were dissolved and stirred until a clear solution was obtained.

[0107] Example 6

[0108] This embodiment provides a lithium battery electrolyte comprising the above-mentioned aromatic asymmetric lithium salt compound 6, which is prepared as follows:

[0109] In an argon-filled glove box, 335g of the above lithium salt compound 6 and 1000mL of propylene carbonate were dissolved and stirred until a clear solution was obtained.

[0110] Example 7

[0111] This embodiment provides a lithium battery electrolyte comprising the above-mentioned aromatic asymmetric lithium salt compound 7, which is prepared as follows:

[0112] In an argon-filled glove box, 299g of the above lithium salt compound 7 and 1000mL of propylene carbonate were dissolved and stirred until a clear solution was obtained.

[0113] Example 8

[0114] This embodiment provides a lithium battery electrolyte comprising the above-mentioned aromatic asymmetric lithium salt compound 8, which is prepared as follows:

[0115] In an argon-filled glove box, 281g of the above lithium salt compound 8 and 1000mL of propylene carbonate were dissolved and stirred until a clear solution was obtained.

[0116] Example 9

[0117] This embodiment provides a lithium battery electrolyte comprising the above-mentioned aromatic asymmetric lithium salt compound 2, which is prepared as follows:

[0118] In an argon-filled glove box, 349g of the above lithium salt compound 2, 500mL of ethylene carbonate, and 500mL of diethyl carbonate were dissolved and stirred until a clear solution was obtained.

[0119] Comparative Example 1

[0120] This comparative example provides a lithium battery electrolyte, which is prepared as follows:

[0121] In an argon-filled glove box, take 287g of lithium bis(trifluoromethanesulfonyl)imide and 1000mL of propylene carbonate, and dissolve and stir until a clear solution is obtained.

[0122] Comparative Example 2

[0123] This comparative example provides a lithium battery electrolyte, which is prepared as follows:

[0124] In an argon-filled glove box, take 287g of lithium bis(trifluoromethanesulfonyl)imide, 500mL of ethylene carbonate, and 500mL of diethyl carbonate, and dissolve and stir until a clear solution is obtained.

[0125] Performance testing

[0126] The electrolyte prepared in Example 1 was used to assemble a battery, and a constant voltage test was performed. The method is as follows:

[0127] Using aluminum foil as the working electrode and lithium foil as the counter electrode, and employing Celgard 2325 separators, button cells were assembled in a glove box and tested after 24 hours of settling. At a constant temperature of 25°C, a constant voltage of 4.3V was maintained for 10 hours, and the change in response current over time was recorded. The test results are shown below. Figure 1 .

[0128] Figure 1 The propylene carbonate solution of lithium salt compound 1 at a concentration of 1 mol / L showed that the stable response current was less than 1 μA under a high voltage of 4.3 V, indicating that lithium salt compound 1 has almost no corrosive behavior on the aluminum foil working electrode.

[0129] The electrolyte prepared in Example 4 was used to assemble a battery, which was then subjected to a constant voltage test using the same method as in Example 1. The test results are shown below. Figure 2 .

[0130] Figure 2 The propylene carbonate solution of lithium salt compound 4 at a concentration of 1 mol / L showed a stable response current of less than 0.1 μA at a high voltage of 4.3 V, indicating that the electrolyte containing lithium salt compound 4 has a better effect on inhibiting aluminum foil corrosion than lithium salt compound 1.

[0131] The electrolyte prepared in Comparative Example 1 was used to assemble a battery, and a constant voltage test was performed using the same method as in Example 1. The test results are shown below. Figure 3 .

[0132] Figure 3 The propylene carbonate solution of LiTFSI at a concentration of 1 mol / L exhibited significant corrosion behavior on the aluminum foil working electrode under a high voltage of 4.3V, with a response current as high as 30 μA after 5 hours and still 16 μA after 10 hours, far exceeding that of Examples 1 and 4. This also indicates that the carbonate-based electrolyte using sulfonylimide lithium salt LiTFSI will continuously corrode the positive electrode current collector, making it unsuitable for large-scale use.

[0133] The test results for other embodiments are shown in Table 1.

[0134] Table 1 summarizes the response currents of Examples (1-8) and Comparative Example 1 during the 4.3V constant voltage test.

[0135] Example 1 ＜1 Example 2 ＜0.3 Example 3 ＜0.2 Example 4 ＜0.1 Example 5 ＜0.5 Example 6 ＜1.2 Example 7 ＜0.4 Example 8 ＜0.2 Comparative Example 1 16

[0136] The electrolytes prepared in Example 9 and Comparative Example 2 were used to assemble batteries, and their cycle performance was tested as follows:

[0137] With LiNi 0.8 Co 0.1 Mn 0.1O2 (NCM811) was used as the positive electrode, lithium foil as the negative electrode, and aluminum foil as the positive current collector. A Celgard 2325 separator was used. Button half-cells were assembled in a glove box and tested after 24 hours of resting. The cells were activated by charging and discharging at 1 / 10C for two cycles at a constant temperature of 25°C, followed by long-term cycling at C / 2 rate. The voltage range was set to 3.0V–4.3V. Test results are shown below. Figure 4 .

[0138] Figure 4 The lithium battery based on lithium salt compound 2 exhibited normal charge and discharge performance with an electrolyte of ethylene carbonate / diethyl carbonate (volume ratio 1:1) at the same lithium salt concentration of 1 mol / L, and a specific capacity of 182.3 mAh g⁻¹ at the C / 2 rate. -1 After 50 cycles, the capacity retention rate was 94%; while the LiTFSI-based lithium battery showed significant capacity decay in the first 5 cycles, with only 44.7 mAh g remaining after the 10th cycle. -1 This indicates that the LiTFSI electrolyte exhibits severe corrosive behavior towards the aluminum foil current collector, causing pores to form on the aluminum foil surface, resulting in the shedding of active material, obstruction of electron and ion transport, and a significant decrease in battery capacity. In contrast, the aromatic asymmetric lithium salt compound 2, thanks to its asymmetric anionic structure, can effectively passivate the aluminum foil current collector under high voltage, ensuring stable battery capacity output.

[0139] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A lithium battery electrolyte, characterized by, It contains aromatic asymmetric lithium salts, organic solvents, optional other lithium salt electrolytes, and optional other additives; The aromatic asymmetric lithium salt is one of the following lithium salt compounds 4 and 8: ； The aromatic asymmetric lithium salt is used as a lithium salt electrolyte and / or additive. When the aromatic asymmetric lithium salt is used as a lithium salt electrolyte, or as a lithium salt electrolyte and additive, the amount of the aromatic asymmetric lithium salt is 0.01~80% based on the mass of the lithium battery electrolyte; When the aromatic asymmetric lithium salt is used only as an additive, the amount of the aromatic asymmetric lithium salt is 0.01~50% based on the mass of the lithium battery electrolyte; The organic solvent is selected from one or more of ethylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, propylene carbonate, vinylene carbonate, fluoroethylene carbonate, diethyl ether, ethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, and methyltetrahydrofuran.

2. The lithium battery electrolyte according to claim 1, wherein, The other lithium salt electrolytes are selected from one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate, lithium trifluoromethanesulfonate, lithium perchlorate, lithium nitrate, lithium sulfate, lithium oxalate, lithium difluorooxalateborate, lithium tetrafluoroborate, and lithium bis(oxalateborate).

3. The lithium battery electrolyte according to claim 1, characterized in that, The other additives are selected from one or more of lithium nitrate, lithium perchlorate, lithium sulfate, lithium oxalate, lithium carbonate, lithium oxide, lithium halide, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate, lithium trifluoromethanesulfonate, lithium difluorooxalateborate, lithium tetrafluoroborate, and lithium bis(oxalateborate).

4. A lithium battery, characterized in that, Includes the lithium battery electrolyte as described in any one of claims 1-3.

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