A perfluoroalkyl quaternary amine additive and use thereof

Abstract

This invention proposes a perfluoroalkyl quaternary ammonium additive having a structure as shown in formula (X): n is an integer between 0 and 7; A is selected from one of nitrate, perchlorate, trifluoroacetate, hexafluorophosphate, tetrafluoroborate, bis(fluorosulfonyl)imide, bis(trifluorosulfonyl)imide, trifluoromethanesulfonate, difluorophosphate, difluorooxalateborate, and oxalate. It has a low LUMO value.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and more specifically, to a perfluoroalkyl quaternary ammonium additive and its application. Background Technology

[0002] Lithium-ion batteries, with their high energy density, long lifespan, and environmental friendliness, have become a core component of consumer electronics, new energy vehicles, and energy storage systems. However, with the continuous expansion of application areas, especially in extreme environments, higher demands are being placed on lithium-ion batteries. Particularly in low-temperature environments, such as polar exploration, aerospace, and special equipment, there is an urgent need for improved low-temperature charge-discharge capabilities and cycle stability. However, conventional carbonate-based electrolytes exhibit significant performance bottlenecks at low temperatures: due to a significantly enhanced polarization effect, the battery's discharge plateau drops sharply, charge-discharge capacity decays rapidly, and rate performance declines. Especially below 0°C, the battery's energy density decreases dramatically, and it may even fail to function properly below -20°C. This limitation in low-temperature performance severely restricts the widespread application of lithium-ion batteries under extreme low-temperature conditions.

[0003] Introducing low-melting-point solvents such as carboxylic acid esters and ethers into existing electrolyte systems can effectively improve the low-temperature performance of lithium batteries because they can reduce electrolyte viscosity and enhance ion conductivity at low temperatures. However, a significant drawback of these solvents is that they weaken battery stability under high-voltage conditions, leading to accelerated electrolyte decomposition and affecting battery life and safety. While low-temperature additives are a simple and effective method to improve low-temperature performance and can optimize interfacial structure and ion migration, current additive technologies have not yet achieved a comprehensive breakthrough in improving electrolyte interfacial film quality, optimizing solvation structure, and enhancing high-voltage stability. Summary of the Invention

[0004] This invention aims to at least partially solve one of the technical problems in the related art. Therefore, one object of this invention is to provide an electrolyte and a lithium-ion battery containing a perfluoroalkyl quaternary ammonium additive, and including the perfluoroalkyl quaternary ammonium additive, to solve the problem that batteries in the prior art cannot simultaneously possess low-temperature performance, high rate capability, and high voltage stability.

[0005] In one aspect of the invention, a perfluoroalkyl quaternary ammonium additive is provided. According to embodiments of the invention, the perfluoroalkyl quaternary ammonium additive has a structure as shown in formula (X):

[0006]

[0007] n is an integer between 0 and 7;

[0008] A is selected from one of the following: nitrate, perchlorate, trifluoroacetate, hexafluorophosphate, tetrafluoroborate, bis(fluorosulfonyl)imide, bis(trifluorosulfonyl)imide, trifluoromethanesulfonate, difluorophosphate, difluorooxalateborate, and oxalate. This perfluoroalkyl quaternary ammonium additive has a low LUMO value and can be preferentially reduced by the solvent to form an inorganic-rich SEI film on the negative electrode surface. This effectively improves the mechanical strength of the SEI film, thereby mitigating side reactions between the electrode and the electrolyte. Simultaneously, anions can preferentially adsorb onto the positive electrode surface, forming a shielding layer that greatly suppresses irreversible side reactions between the high-voltage positive electrode and the solvent, thus significantly improving the cycle stability of high-voltage lithium batteries.

[0009] According to embodiments of the present invention, the above-mentioned perfluoroalkyl quaternary ammonium additive may further include at least one of the following negative electrode technical features:

[0010] According to an embodiment of the present invention, n is 0, 1, 2, 3, 4, 5, 6 or 7.

[0011] According to embodiments of the present invention, the perfluoroalkyl quaternary ammonium additive has one of the following structures:

[0012]

[0013] In another aspect, the present invention also provides an electrolyte. According to an embodiment of the invention, the electrolyte comprises a perfluoroalkyl quaternary ammonium additive having the structure shown in formula (X):

[0014]

[0015] n is an integer between 0 and 7;

[0016] A is selected from one of the following: nitrate, perchlorate, trifluoroacetate, hexafluorophosphate, tetrafluoroborate, bis(fluorosulfonyl)imide, bis(trifluorosulfonyl)imide, trifluoromethanesulfonate, difluorophosphate, difluorooxalateborate, and oxalate.

[0017] According to embodiments of the present invention, the electrolyte may further include at least one of the following additional technical features:

[0018] According to embodiments of the present invention, the perfluoroalkyl quaternary ammonium additive has one of the following structures:

[0019]

[0020] According to embodiments of the present invention, the concentration of the perfluoroalkyl quaternary ammonium additive is 0.1 wt% to 5 wt%.

[0021] According to an embodiment of the present invention, the electrolyte further comprises an electrolyte lithium salt, an organic solvent, a low-temperature additive, and a functional additive.

[0022] According to an embodiment of the present invention, the lithium salt electrolyte is one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium tetrafluoroborate, and lithium hexafluorophosphate.

[0023] According to an embodiment of the present invention, the concentration of the electrolyte lithium salt is 0.01 to 5 mol / L.

[0024] According to embodiments of the present invention, the organic solvent is one or more selected from ethylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, propylene carbonate, vinylene carbonate, fluoroethylene carbonate, tetrahydrofuran, diethyl ether, ethylene glycol dimethyl ether, dipropyl ether, 1,2-dimethoxypropane, 1,3-dioxolane, 2-methyltetrahydrofuran, cyclopentylmethyl ether, tetrahydropyran, 1,3-dioxane, and 1,4-dioxane.

[0025] According to an embodiment of the present invention, the functional additive is one or more of lithium nitrate, lithium difluorooxalate borate, tris(trimethylsilane)borate, tris(trimethylsilane)phosphate, and lithium difluorophosphate.

[0026] According to an embodiment of the present invention, the concentration of the functional additive is 0.1 wt% to 5 wt%.

[0027] In another aspect, the present invention also provides a battery. According to an embodiment of the present invention, the battery comprises the electrolyte described above. The lithium-ion battery of the present invention is not limited in form and can be cylindrical, aluminum-cased, plastic-cased, or pouch-type.

[0028] According to embodiments of the present invention, the battery may further include at least one of the following additional technical features:

[0029] According to an embodiment of the present invention, the battery is a lithium-ion battery.

[0030] According to an embodiment of the present invention, the battery further includes a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode.

[0031] According to embodiments of the present invention, the cathode is a lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese oxide, or a ternary cathode material.

[0032] According to an embodiment of the present invention, the cathode is a ternary cathode material, such as LiNi. x Co y Mn 1-x-y O2, where 0 < x < 1, 0 < y < 1, and x + y < 1.

[0033] According to an embodiment of the present invention, the negative electrode is a lithium metal negative electrode, a graphite negative electrode, or a silicon-carbon negative electrode.

[0034] According to an embodiment of the present invention, the diaphragm is a polypropylene or polyethylene film.

[0035] According to embodiments of the present invention, the present invention has the following technical effects:

[0036] The perfluoroalkyl quaternary ammonium additive of this invention has a low LUMO value and can be preferentially reduced by the solvent to form an SEI film rich in inorganic components on the surface of the negative electrode. This can effectively improve the mechanical strength of the SEI film, thereby alleviating the side reactions between the electrode and the electrolyte. At the same time, anions can be preferentially adsorbed on the surface of the positive electrode to form a shielding layer, which greatly suppresses the irreversible side reactions between the high-voltage positive electrode and the solvent, thereby significantly improving the cycle stability of the high-voltage lithium battery. Attached Figure Description

[0037] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0038] Figure 1 The graph shows the -60°C low-temperature cycling performance of the NCM811 / Li batteries prepared by Example 1, Comparative Example 1, and Comparative Example 2.

[0039] Figure 2 The discharge curves of the 500mAh NCM811 / Li pouch cell prepared in Example 1 at different rates at -50℃ are shown. Detailed Implementation

[0040] The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0041] The organic solvents, lithium salt electrolytes, and additives used in the embodiments and comparative examples of this invention are all battery grade. The perfluoroalkyl quaternary ammonium additives prepared in this invention undergo multiple purification steps and strict drying.

[0042] In the following examples, the electrolyte was prepared in a glove box filled with 99.999% pure argon gas, with a moisture content of less than 0.1 ppm, at room temperature.

[0043] Example 1

[0044] This embodiment provides a product containing the above-mentioned perfluoroalkyl quaternary ammonium additive I. The lithium battery electrolyte is prepared as follows:

[0045] In an argon-filled glove box, take 187g of lithium difluorosulfonylimide, 9.13g of the above-mentioned perfluoroalkyl quaternary ammonium additive I, 9.13g of tris(trimethylsilane)borate, 100mL of ethylene glycol dimethyl ether, and 900mL of diethyl ether, and stir until a homogeneous, clear, and transparent solution is obtained.

[0046] Example 2

[0047] This embodiment provides a product containing the above-mentioned perfluoroalkyl quaternary ammonium additive II. The lithium battery electrolyte is prepared as follows:

[0048] In an argon-filled glove box, take 187g of lithium bis(trifluorosulfonyl)imide, 9.13g of the above-mentioned perfluoroalkyl quaternary ammonium additive II, 9.13g of tris(trimethylsilane)borate, 100mL of ethylene glycol dimethyl ether, and 900mL of diethyl ether, and stir until a homogeneous, clear, and transparent solution is obtained.

[0049] Example 3

[0050] This embodiment provides a product containing the above-mentioned perfluoroalkyl quaternary ammonium additive III. The lithium battery electrolyte is prepared as follows:

[0051] In an argon-filled glove box, take 187g of lithium difluorosulfonylimide, 9.13g of the above-mentioned perfluoroalkyl quaternary ammonium additive III, 9.13g of tris(trimethylsilane)borate, 100mL of ethylene glycol dimethyl ether, and 900mL of diethyl ether, and stir until a homogeneous, clear, and transparent solution is obtained.

[0052] Example 4

[0053] This embodiment provides a lithium battery electrolyte containing the above-mentioned perfluoroalkyl quaternary ammonium additive I, which is prepared as follows:

[0054] In an argon-filled glove box, take 187g of lithium difluorosulfonylimide, 9.13g of the above-mentioned perfluoroalkyl quaternary ammonium additive I, 9.13g of tris(trimethylsilane)borate, 100mL of ethylene glycol dimethyl ether, and 900mL of 1,4-dioxane and stir until a homogeneous, clear, and transparent solution is obtained.

[0055] Example 5

[0056] This embodiment provides a lithium battery electrolyte containing the above-mentioned perfluoroalkyl quaternary ammonium additive I, which is prepared as follows:

[0057] In an argon-filled glove box, take 187g of lithium difluorosulfonylimide, 9.13g of the above-mentioned perfluoroalkyl quaternary ammonium additive I, 9.13g of tris(trimethylsilane)borate, 100mL of ethylene glycol dimethyl ether, and 900mL of tetrahydropyran, and stir until a homogeneous, clear, and transparent solution is obtained.

[0058] Comparative Example 1

[0059] This comparative example provides a lithium battery electrolyte, which is prepared as follows:

[0060] In an argon-filled glove box, take 187g of lithium difluorosulfonylimide, 9.13g of tris(trimethylsilane)borate, 100mL of ethylene glycol dimethyl ether, and 900mL of diethyl ether, and stir until a homogeneous, clear, and transparent solution is obtained.

[0061] Comparative Example 2

[0062] This comparative example provides a lithium battery electrolyte, which is prepared as follows:

[0063] In an argon-filled glove box, take 187g of lithium bis(trifluorosulfonyl)imide, 10.13g of tris(trimethylsilane)borate, 100mL of ethylene glycol dimethyl ether, and 900mL of tetrahydropyran, and stir until a homogeneous, clear, and transparent solution is obtained.

[0064] Comparative Example 3

[0065] This comparative example provides a lithium battery electrolyte, which is prepared as follows:

[0066] In an argon-filled glove box, take 187g of lithium difluorosulfonylimide, 9.13g of tris(trimethylsilane)borate, 100mL of ethylene glycol dimethyl ether, and 900mL of 1,4-dioxane and stir until a homogeneous, clear, and transparent solution is obtained.

[0067] Comparative Example 4

[0068] This comparative example provides a lithium battery electrolyte, which is prepared as follows:

[0069] In an argon-filled glove box, take 187g of lithium difluorosulfonylimide, 9.13g of tris(trimethylsilane)borate, and 100mL of ethylene glycol dimethyl ether and stir until a homogeneous, clear, and transparent solution is obtained.

[0070] Comparative Example 5

[0071] This comparative example provides a lithium battery electrolyte, which is prepared as follows:

[0072] In an argon-filled glove box, take 152g of lithium hexafluorophosphate, 500mL of ethylene carbonate, and 500mL of dimethyl carbonate, and stir until a homogeneous, clear, and transparent solution is obtained.

[0073] Performance testing

[0074] The electrolytes prepared in the above embodiments and comparative examples were assembled into batteries and then subjected to cycle performance tests. The methods are as follows: The electrolytes prepared in the above embodiments and comparative examples were assembled into batteries and then subjected to cycle performance tests. The methods are as follows: Using LiNi0.8 Co 0.1 Mn 0.1 O2 (NCM811) was used as the positive electrode, lithium foil as the negative electrode, and aluminum foil as the current collector. Celgard 2325 separators were used. Button and pouch batteries were assembled in a glove box and then tested after settling. First, the batteries were activated by charging and discharging at 1 / 10C from 3.0V to 4.3V at a constant temperature of 25℃. Then, they were discharged at different rates at -50℃. The test results are shown in Table 1 and Appendix. Figure 1 The cycle performance at -60℃ with 0.05C charge and 0.1C discharge is shown in Table 2 and Appendix. Figure 2 .

[0075] Table 1. Discharge capacity of NCM811 / Li half-cells assembled in the examples and comparative examples at different temperatures.

[0076]

[0077] Table 2. Discharge capacity of the 500mAh soft pack at -50°C for the examples and comparative examples.

[0078]

[0079] From Tables 1-2 and Figures 1-2 As can be seen, when performing charge-discharge cycles at low temperatures, the electrolyte prepared in this embodiment of the invention exhibits significantly better capacity, cycle stability, and capacity retention at different rates at -50°C than the comparative example at -60°C. This indicates that the perfluoroalkyl quaternary ammonium additive provided by this invention can significantly improve the low-temperature cycle stability of the battery and achieve excellent low-temperature discharge characteristics.

[0080] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0081] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. An electrolyte, characterized by, The electrolyte comprises a perfluoroalkyl quaternary ammonium additive having one of the following structures: 、 、 ； The concentration of the perfluoroalkyl quaternary ammonium additive is 0.1wt%-5wt%. The electrolyte further comprises an electrolyte lithium salt, an organic solvent, a low-temperature additive, and a functional additive. The organic solvent is ethylene glycol dimethyl ether and diethyl ether.

2. The electrolyte according to claim 1, characterized in that, The lithium salt electrolyte is one or more of lithium bisfluorosulfonylimide, lithium bis-trifluoromethylsulfonylimide, lithium trifluoromethylsulfonate, lithium tetrafluoroborate, and lithium hexafluorophosphate. The concentration of the electrolyte lithium salt is 0.01-5mol / L.

3. The electrolyte of claim 1, wherein The functional additive is one or more of lithium nitrate, lithium bisfluoroxalate borate, tris(trimethylsilyl) borate, tris(trimethylsilyl) phosphate, and lithium difluorophosphate. The concentration of the functional additive is 0.1wt%-5wt%.

4. A battery, characterized by The battery comprises the electrolyte of any one of claims 1-3.

5. The battery of claim 4, wherein, The battery is a lithium ion battery.

6. The battery of claim 4, wherein, The battery further comprises a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode.

7. The battery of claim 6, wherein, The positive electrode is lithium iron phosphate, lithium cobaltate, lithium manganate, lithium nickel manganate, or a ternary positive electrode material.

8. The battery of claim 6, wherein, The negative electrode is a lithium metal negative electrode, graphite, or a silicon-carbon negative electrode.

9. The battery of claim 6, wherein, The separator is a polypropylene or polyethylene film.

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