Perfluoroalkyl quaternary amine additive and application thereof

Abstract

The invention provides a perfluoroalkyl quaternary amine additive. The perfluoroalkyl quaternary amine additive has a structure as shown in a formula (X): # imgabs0 # n is an integer between 0 and 7; a is selected from one of nitrate radical, perchlorate radical, trifluoroacetate radical, hexafluorophosphate radical, tetrafluoroborate radical, bis (fluorosulfonyl) imide, bis (trifluorosulfonyl) imide, trifluoromethanesulfonate radical, difluorophosphate radical, difluoro (oxalato) borate radical and oxalate radical. The polymer has a low LUMO value.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a perfluoroalkyl quaternary amine additive and application thereof. Background Art

[0002] Lithium-ion batteries have become a core component of consumer electronics, new energy vehicles and energy storage systems due to their high energy density, long life and environmental friendliness. However, with the continuous expansion of application areas, higher requirements are placed on lithium-ion batteries, especially in extreme environments. In particular, in low-temperature environments, such as polar exploration, aerospace, and special equipment, there is an urgent need for the low-temperature charging and discharging capabilities and cycle stability of batteries. However, conventional carbonate-based electrolytes exhibit a large performance bottleneck at low temperatures: due to the significantly enhanced polarization effect, the battery's discharge platform drops sharply, the charge and discharge capacity decays rapidly, and the rate performance decreases, especially below 0°C. The energy density of the battery is greatly reduced, and it cannot even work properly below -20°C. This limitation in low-temperature performance has greatly restricted the widespread application of lithium-ion batteries under extreme low-temperature conditions.

[0003] Introducing solvents with lower melting points, such as carboxylic acid esters and ether solvents, into existing electrolyte systems can effectively improve the low-temperature performance of lithium batteries because they can reduce the viscosity of the electrolyte and enhance ion conductivity at low temperatures. However, a significant disadvantage of this type of solvent is that it weakens the stability of the battery under high voltage conditions, leading to accelerated decomposition of the electrolyte, affecting the life and safety of the battery. As a simple and effective method to improve low-temperature performance, low-temperature additives can optimize the interface structure and ion migration, but current additive technology has not yet achieved a comprehensive breakthrough in improving the quality of the electrolyte interface film, optimizing the solvation structure, and improving high-voltage stability. Summary of the invention

[0004] The present invention aims to solve one of the technical problems in the related art at least to a certain extent. To this end, one object of the present invention is to provide a perfluoroalkyl quaternary amine additive, an electrolyte and a lithium ion battery comprising the perfluoroalkyl quaternary amine additive, so as to solve the problem that the battery in the prior art cannot have both low temperature performance, high rate and high voltage stability.

[0005] In one aspect of the present invention, the present invention provides a perfluoroalkyl quaternary amine additive. According to an embodiment of the present invention, the perfluoroalkyl quaternary amine 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 nitrate, perchlorate, trifluoroacetate, hexafluorophosphate, tetrafluoroborate, bisfluorosulfonyl imide, bistrifluorosulfonyl imide, trifluoromethanesulfonate, difluorophosphate, difluorooxalatoborate, and oxalate. The perfluoroalkyl quaternary amine additive has a lower LUMO value, can be preferentially reduced by the solvent, and forms a SEI film rich in inorganic components on the surface of the negative electrode, which can effectively improve the mechanical strength of the SEI film, thereby alleviating the side reaction between the electrode and the electrolyte. At the same time, the anion can be preferentially adsorbed on the surface of the positive electrode to form a shielding layer, which greatly inhibits the irreversible side reaction between the high-voltage positive electrode and the solvent, thereby significantly improving the cycle stability of the high-voltage lithium battery.

[0009] According to an embodiment of the present invention, the above-mentioned perfluoroalkyl quaternary amine 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 an embodiment of the present invention, the perfluoroalkyl quaternary amine additive has one of the following structures:

[0012]

[0013] In another aspect of the present invention, the present invention further provides an electrolyte. According to an embodiment of the present invention, the electrolyte includes a perfluoroalkyl quaternary amine additive, and the perfluoroalkyl quaternary amine additive has a structure shown in formula (X):

[0014]

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

[0016] A is selected from the group consisting of nitrate, perchlorate, trifluoroacetate, hexafluorophosphate, tetrafluoroborate, bisfluorosulfonyl imide, bistrifluorosulfonyl imide, trifluoromethanesulfonate, difluorophosphate, difluorooxalatoborate, and oxalate.

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

[0018] According to an embodiment of the present invention, the perfluoroalkyl quaternary amine additive has one of the following structures:

[0019]

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

[0021] According to an embodiment of the present invention, the electrolyte further includes electrolyte lithium salt, organic solvent, low temperature additive and 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(trifluoromethylsulfonyl)imide, lithium trifluoromethylsulfonate, lithium tetrafluoroborate, and lithium hexafluorophosphate.

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

[0024] According to an embodiment of the present invention, the organic solvent is one or more of ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, propylene carbonate, vinylene carbonate, fluoroethylene carbonate, tetrahydrofuran, ethyl ether, ethylene glycol dimethyl ether, dipropyl ether, 1,2-dimethoxypropane, 1,3-dioxolane, 2-methyltetrahydrofuran, cyclopentyl methyl 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 difluorooxalatoborate, tris(trimethylsilyl)borate, tris(trimethylsilyl)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 of the present invention, the present invention further provides a battery. According to an embodiment of the present invention, the battery comprises the electrolyte described above. The shape of the lithium-ion battery of the present invention is not limited, and can be a cylinder, an aluminum shell, a plastic shell or a soft package shell.

[0028] According to an embodiment of the present invention, the above 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 an embodiment of the present invention, the positive electrode is lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese oxide or a ternary positive electrode material.

[0032] According to an embodiment of the present invention, the positive electrode is a ternary positive electrode material. For example, 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 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 the embodiments of the present invention, the present invention has the following technical effects:

[0036] The perfluoroalkyl quaternary amine additive of the present invention has a lower LUMO value and can be preferentially reduced by a solvent to form an SEI film rich in inorganic components on the surface of the negative electrode, which can effectively improve the mechanical strength of the SEI film, thereby alleviating the side reaction 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 inhibits the irreversible side reaction between the high-voltage positive electrode and the solvent, thereby significantly improving the cycle stability of the high-voltage lithium battery. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0038] Figure 1 The -60°C low temperature cycle performance diagram of the NCM811 / Li battery prepared by Example 1, Comparative Example 1 and Comparative Example 2;

[0039] Figure 2 1 and 2 are discharge curves of the 500mAh NCM811 / Li soft-pack battery prepared in Example 1 at different rates at -50°C. DETAILED DESCRIPTION

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

[0041] The organic solvents, lithium salt electrolytes and additives used in the examples and comparative examples of the present invention are all of battery grade, and the perfluoroalkyl quaternary amine additives prepared in the present invention are subjected to multi-step purification and strict drying.

[0042] The electrolyte preparation conditions in the following examples are as follows: the electrolyte is prepared in a glove box filled with argon gas with a purity of 99.999%, the moisture in the glove box is less than 0.1 ppm, and the temperature is room temperature.

[0043] Example 1

[0044] This embodiment provides a perfluoroalkyl quaternary amine additive I The lithium battery electrolyte is prepared as follows:

[0045] In a glove box filled with argon, 187 g of lithium bis(fluorosulfonyl)imide, 9.13 g of the above-mentioned perfluoroalkyl quaternary amine additive I, 9.13 g of tris(trimethylsilyl)borate, 100 mL of ethylene glycol dimethyl ether, and 900 mL of ether were stirred until a uniform, clear and transparent solution was obtained.

[0046] Example 2

[0047] This embodiment provides a perfluoroalkyl quaternary amine additive II The lithium battery electrolyte is prepared as follows:

[0048] In a glove box filled with argon, 187 g of lithium bis(trifluorosulfonyl)imide, 9.13 g of the above-mentioned perfluoroalkyl quaternary amine additive II, 9.13 g of tris(trimethylsilyl)borate, 100 mL of ethylene glycol dimethyl ether, and 900 mL of ether were stirred until a uniform, clear and transparent solution was obtained.

[0049] Example 3

[0050] This embodiment provides a perfluoroalkyl quaternary amine additive III The lithium battery electrolyte is prepared as follows:

[0051] In a glove box filled with argon, 187 g of lithium bis(fluorosulfonyl)imide, 9.13 g of the above-mentioned perfluoroalkyl quaternary amine additive III, 9.13 g of tris(trimethylsilyl)borate, 100 mL of ethylene glycol dimethyl ether, and 900 mL of ether were stirred until a uniform, clear and transparent solution was obtained.

[0052] Example 4

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

[0054] In a glove box filled with argon, 187 g of lithium bis(fluorosulfonyl)imide, 9.13 g of the above-mentioned perfluoroalkyl quaternary amine additive I, 9.13 g of tris(trimethylsilyl)borate, 100 mL of ethylene glycol dimethyl ether, and 900 mL of 1,4-dioxane were stirred until a uniform, clear and transparent solution was obtained.

[0055] Example 5

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

[0057] In a glove box filled with argon, 187 g of lithium bis(fluorosulfonyl)imide, 9.13 g of the above-mentioned perfluoroalkyl quaternary amine additive I, 9.13 g of tris(trimethylsilyl)borate, 100 mL of ethylene glycol dimethyl ether, and 900 mL of tetrahydropyran were stirred until a uniform, clear and transparent solution was obtained.

[0058] Comparative Example 1

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

[0060] In a glove box filled with argon, 187 g of lithium bis(fluorosulfonyl)imide, 9.13 g of tris(trimethylsilyl)borate, 100 mL of ethylene glycol dimethyl ether, and 900 mL of ether were stirred until a homogeneous, clear, and transparent solution was obtained.

[0061] Comparative Example 2

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

[0063] In a glove box filled with argon, 187 g of lithium bis(trifluorosulfonyl)imide, 10.13 g of tris(trimethylsilyl)borate, 100 mL of ethylene glycol dimethyl ether, and 900 mL of tetrahydropyran were stirred until a homogeneous, clear, and transparent solution was obtained.

[0064] Comparative Example 3

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

[0066] In a glove box filled with argon, 187 g of lithium bis(fluorosulfonyl)imide, 9.13 g of tris(trimethylsilyl)borate, 100 mL of ethylene glycol dimethyl ether, and 900 mL of 1,4-dioxane were stirred until a uniform, clear, transparent solution was obtained.

[0067] Comparative Example 4

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

[0069] In a glove box filled with argon, 187 g of lithium bis(fluorosulfonyl)imide, 9.13 g of tris(trimethylsilyl)borate, and 100 mL of ethylene glycol dimethyl ether were stirred until a uniform, clear, transparent solution was obtained.

[0070] Comparative Example 5

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

[0072] In a glove box filled with argon, take 152 g of lithium hexafluorophosphate, 500 mL of ethylene carbonate, and 500 mL of dimethyl carbonate, and stir until a uniform, 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 the cycle performance was tested. The method is as follows: The electrolytes prepared in the above embodiments and comparative examples were assembled into batteries and then the cycle performance was tested. The method is as follows: LiNi0.8 Co 0.1 Mn 0.1 O2 (NCM811) is the positive electrode, lithium sheet is the negative electrode, aluminum foil is the current collector, and Celgard2325 is used as the separator. The button cell and soft pack cell are assembled in the glove box and tested after standing. First, the battery is activated by charging and discharging at 1 / 10C 3.0V to 4.3V at room temperature 25℃, and then discharged at different rates at -50℃. The test results are shown in Table 1 and Appendix. Figure 1 The test results of the cycle performance at -60°C with 0.05C charge and 0.1C discharge are 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 500mAh soft packs assembled in the examples and comparative examples at different rates at -50°C

[0078]

[0079] From Tables 1 to 2 and Figures 1-2 It can be seen that when the charge and discharge cycle is carried out at low temperature, the capacity, cycle stability at -60°C and the capacity retention rate at different rates at -50°C of the electrolyte prepared in the embodiment of the present invention are significantly better than those of the comparative example, indicating that the perfluoroalkyl quaternary amine additive provided by the invention can significantly improve the low-temperature cycle stability of the battery and obtain excellent low-temperature discharge characteristics.

[0080] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0081] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A perfluoroalkyl quaternary amine additive, characterized in that: Having a structure as shown in formula (X): n is an integer between 0 and 7; A is selected from the group consisting of nitrate, perchlorate, trifluoroacetate, hexafluorophosphate, tetrafluoroborate, bisfluorosulfonyl imide, bistrifluorosulfonyl imide, trifluoromethanesulfonate, difluorophosphate, difluorooxalatoborate, and oxalate.

2. The perfluoroalkyl quaternary amine additive according to claim 1, characterized in that: It is one of the following structures:

3. An electrolyte, characterized in that: The electrolyte includes a perfluoroalkyl quaternary amine additive, and the perfluoroalkyl quaternary amine additive has a structure shown in formula (X): n is an integer between 0 and 7; A is selected from the group consisting of nitrate, perchlorate, trifluoroacetate, hexafluorophosphate, tetrafluoroborate, bisfluorosulfonyl imide, bistrifluorosulfonyl imide, trifluoromethanesulfonate, difluorophosphate, difluorooxalatoborate, and oxalate.

4. The electrolyte according to claim 3, characterized in that The perfluoroalkyl quaternary amine additive has one of the following structures: Optionally, the concentration of the perfluoroalkyl quaternary amine additive is 0.1 wt% to 5 wt%.

5. The electrolyte according to claim 3, characterized in that The electrolyte further includes electrolyte lithium salt, organic solvent, low temperature additive and functional additive.

6. The electrolyte according to claim 5, characterized in that The lithium salt electrolyte is one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium trifluoromethylsulfonate, lithium tetrafluoroborate, and lithium hexafluorophosphate; Optionally, the concentration of the electrolyte lithium salt is 0.01 to 5 mol / L.

7. The electrolyte according to claim 5, characterized in that The organic solvent is one or more of ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, propylene carbonate, vinylene carbonate, fluoroethylene carbonate, tetrahydrofuran, ethyl ether, ethylene glycol dimethyl ether, dipropyl ether, 1,2-dimethoxypropane, 1,3-dioxolane, 2-methyltetrahydrofuran, cyclopentyl methyl ether, tetrahydropyran, 1,3-dioxane, and 1,4-dioxane.

8. The electrolyte according to claim 5, characterized in that The functional additive is one or more of lithium nitrate, lithium difluorooxalatoborate, tris(trimethylsilyl)borate, tris(trimethylsilyl)phosphate, and lithium difluorophosphate; Optionally, the concentration of the functional additive is 0.1 wt% to 5 wt%.

9. A battery, characterized in that: The battery comprises the electrolyte according to any one of claims 5 to 8.

10. The battery according to claim 9, characterized in that The battery is a lithium-ion battery; Optionally, the battery further comprises a positive electrode, a negative electrode and a separator disposed between the positive electrode and the negative electrode; Optionally, the positive electrode is lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese oxide or a ternary positive electrode material; Optionally, the negative electrode is a lithium metal negative electrode, a graphite or a silicon carbon negative electrode; Optionally, the separator is a polypropylene or polyethylene film.

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