Electrolyte and battery

Abstract

The invention provides an electrolyte and a battery, the electrolyte comprises a lithium salt, an organic solvent and an additive, and functional groups of the additive comprise a silicon group, a fluorine-containing alkyl group, an amino group and a sulfonate group. The additive containing the silicon base, the fluorine-containing alkyl group, the amino group and the sulfonate group is added into the electrolyte, and the silicon base in the additive can inhibit corrosion of moisture, HF and residual alkali substances to a positive electrode material and decomposition of the electrolyte; the fluorine-containing alkyl group can promote formation of a stable SEI film and reduce charge transfer impedance; the amino group can generate coordination with high-valence metal ions of the positive electrode to form a complex, so that the oxygenolysis of the positive electrode material on the electrolyte can be reduced; and the sulfonate group can participate in film formation, and the formed interfacial film can reduce the interfacial impedance, so that the cycle performance of the lithium ion battery can be improved.

Description

Technical Field

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

[0002] Lithium-ion batteries have the advantages of high energy density, no memory effect, long service life, clean and pollution-free, and are widely used in various fields, including mobile phones, laptops, new energy vehicles, etc. However, with the expansion of human activities, higher requirements are placed on the performance of lithium-ion batteries, especially the cycle performance.

[0003] As an important component of lithium-ion batteries, electrolyte plays an irreplaceable role in the cycle performance of lithium-ion batteries. Research generally believes that the most economical and effective technical means to improve the cycle performance of lithium-ion batteries is to add additives to the electrolyte. The effect of existing additives on improving the cycle performance of lithium-ion batteries needs to be improved. Summary of the invention

[0004] The embodiments of the present invention provide an electrolyte and a battery, which can improve the cycle performance of existing lithium-ion batteries.

[0005] In a first aspect, an embodiment of the present invention provides an electrolyte comprising a lithium salt, an organic solvent and an additive, wherein the functional groups of the additive comprise a silicon group, a fluorinated alkyl group, an amino group and a sulfonate group.

[0006] In one embodiment, the additive is tris(dimethylamino)silyl trifluoromethanesulfonate; and / or

[0007] The lithium salt is at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium difluorophosphate, lithium difluorooxalatephosphate, and lithium dioxalateborate.

[0008] In one embodiment, the mass content of the lithium salt in the electrolyte is 10-15%; and / or

[0009] The mass content of the tris(dimethylamino)silyl trifluoromethanesulfonate in the electrolyte is 0.3-1.0%.

[0010] In one embodiment, the organic solvent includes dimethyl carbonate, ethyl methyl carbonate, ethylene carbonate and propylene carbonate, and the mass ratio of the dimethyl carbonate, the ethyl methyl carbonate, the ethylene carbonate and the propylene carbonate is (30-50):(20-30):(20-30):(1-10).

[0011] In one embodiment, the electrolyte further includes a film-forming protective agent.

[0012] In one embodiment, the mass content of the film-forming protective agent in the electrolyte is 2-4%; and / or

[0013] The film-forming protective agent includes at least one of vinylene trithiocarbonate, vinyl sulfate, vinyl carbonate, vinylene carbonate, and fluoroethylene carbonate.

[0014] In one embodiment, the film-forming protective agent includes vinylene carbonate and vinyl sulfate.

[0015] In one embodiment, the mass ratio of vinylene carbonate to vinyl sulfate is (4-6):(1-2).

[0016] In a second aspect, an embodiment of the present invention provides a battery, comprising the above-mentioned electrolyte.

[0017] In one embodiment, the battery includes a positive electrode, the chemical formula of the active material of the positive electrode is LiMn x Fe 1- x PO4, where 0<x<1.

[0018] Beneficial effects of the embodiments of the present invention:

[0019] In an embodiment of the present invention, by adding an additive containing a silicon group, a fluorinated alkyl group, an amino group and a sulfonate group to the electrolyte, the silicon group in the additive can remove moisture, HF and residual alkaline substances in the positive electrode material, thereby inhibiting the corrosion of moisture, HF and residual alkaline substances to the positive electrode material and the decomposition of the electrolyte; the fluorinated alkyl group can increase the reduction potential of the electrolyte, thereby promoting the formation of a stable SEI film and reducing the charge transfer impedance; the nitrogen atoms of the amino group each have a pair of lone pairs of electrons, which can coordinate with the high-valent metal atoms (such as iron ions and manganese ions) of the positive electrode to form a complex, thereby reducing the oxidative decomposition of the electrolyte by the positive electrode material; the sulfonate group can participate in film formation, and the interface film formed by it can reduce the interface impedance, thereby improving the cycle performance of the lithium-ion battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0021] Figure 1 It is the structural formula of tris(dimethylamino)silyl trifluoromethanesulfonate provided in the embodiments of the present invention. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention. In addition, it should be understood that the specific implementation methods described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention. In the present invention, unless otherwise specified, the directional words used, such as "upper" and "lower", generally refer to the upper and lower parts of the device in actual use or working state, specifically the drawing direction in the drawings; while "inside" and "outside" refer to the outline of the device.

[0023] The technical solution of this application is as follows:

[0024] In a first aspect, an embodiment of the present application provides an electrolyte comprising a lithium salt, an organic solvent and an additive, wherein the functional groups of the additive comprise a silicon group, a fluorinated alkyl group, an amino group and a sulfonate group.

[0025] In the present application, by adding additives to the electrolyte, the silicon group in the additive can remove moisture, HF and residual alkali substances in the positive electrode material, thereby inhibiting the corrosion of moisture, HF and residual alkali substances to the positive electrode material and the decomposition of the electrolyte; the fluorinated alkyl group can increase the reduction potential of the electrolyte, thereby promoting the formation of a stable solid electrolyte interphase (SEI film) and reducing the charge transfer impedance; the nitrogen atoms of the amino group each have a pair of lone pairs of electrons, which can coordinate with the high-valent metal ions (such as iron ions and manganese ions) of the positive electrode to form a complex, thereby reducing the oxidative decomposition of the electrolyte by the positive electrode material; the sulfonate group can participate in film formation, and the interface film formed by it can reduce the interface impedance, thereby improving the cycle performance of the lithium-ion battery.

[0026] In some embodiments, the additive is tris(dimethylamino)silyl trifluoromethanesulfonate.

[0027] In the present application, tris(dimethylamino)silyl trifluoromethanesulfonate (whose structural formula is as follows) is added to the electrolyte. Figure 1 As shown, the molecular formula is C7H 18F3N3O3SSi, CAS No. 155166-32-8), which has multiple functional groups including silicon group, fluorinated alkyl group, amino group and sulfonate group, wherein the silicon group can remove moisture, HF and residual alkali substances in the positive electrode material, thereby inhibiting the corrosion of moisture, HF and residual alkali substances to the positive electrode material and the decomposition of the electrolyte; the fluorinated alkyl group can increase the reduction potential of the electrolyte, thereby promoting the formation of a stable SEI film and reducing the charge transfer impedance; the nitrogen atoms of the three amino groups each have a pair of lone pairs of electrons, which can coordinate with the high-valent metal ions (such as iron ions and manganese ions) of the positive electrode to form a complex, thereby reducing the oxidative decomposition of the electrolyte by the positive electrode material; the sulfonate group can participate in film formation, and the interface film formed by it can reduce the interface impedance, thereby improving the cycle performance of the lithium-ion battery.

[0028] In some embodiments, the mass content of the tris(dimethylamino)silyl trifluoromethanesulfonate in the electrolyte is 0.3-1.0%, for example, it can be 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, etc. Within the range, tris(dimethylamino)silyl trifluoromethanesulfonate can improve the DC impedance of the battery, thereby improving the cycle performance of the lithium-ion battery.

[0029] In some embodiments, the organic solvent includes dimethyl carbonate, ethyl methyl carbonate, ethylene carbonate, and propylene carbonate.

[0030] In some embodiments, the mass ratio of the dimethyl carbonate, the ethyl methyl carbonate, the ethylene carbonate and the propylene carbonate is (30-50):(20-30):(20-30):(1-10).

[0031] In some embodiments, the mass ratio of the dimethyl carbonate, the ethyl methyl carbonate, the ethylene carbonate and the propylene carbonate is 30:30:30:10.

[0032] In some embodiments, the lithium salt is at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium difluorophosphate, lithium difluorooxalatephosphate, and lithium dioxalateborate.

[0033] In some embodiments, the lithium salt has a mass content of 10-15% in the electrolyte.

[0034] In some embodiments, the electrolyte further includes a film-forming protective agent.

[0035] In some embodiments, the mass content of the film-forming protective agent in the electrolyte is 2-4%.

[0036] In some embodiments, the film-forming protective agent includes at least one of vinylene trithiocarbonate, vinyl sulfate, vinyl carbonate, vinylene carbonate, and fluoroethylene carbonate.

[0037] In some embodiments, the film-forming protective agent includes vinylene carbonate and vinyl sulfate.

[0038] In the present application, vinylene carbonate (VC) and diethylene sulfate (DTD) can improve the DC impedance of the battery and thus improve the cycle performance of the lithium-ion battery.

[0039] In some embodiments, the mass ratio of vinylene carbonate (VC) to diethylene sulfate (DTD) is (4-6): (1-2).

[0040] In a second aspect, an embodiment of the present application provides a battery, comprising the above-mentioned electrolyte.

[0041] In some embodiments, the battery includes a positive electrode, the active material of the positive electrode having a chemical formula of LiMn x Fe 1- x PO4, where 0<x<1. In this way, the active material of the positive electrode has a high potential and a stronger coordination effect with the amino group in the additive.

[0042] Example 1

[0043] An electrolyte and a preparation method thereof, comprising the following steps:

[0044] In a glove box filled with argon, LiPF6 was dissolved in a mixed solution of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), ethylene carbonate (EC) and propylene carbonate (PC) in a mass ratio of 30:30:30:10, and then vinylene carbonate (VC) and vinyl sulfate (DTD) were added, and finally tris(dimethylamino)silyl trifluoromethanesulfonate was added. After stirring evenly, an electrolyte was obtained, in which the mass content of LiPF6 was 12.5%, the mass content of VC was 3%, the mass content of DTD was 1%, and the mass content of tris(dimethylamino)silyl trifluoromethanesulfonate was 1%.

[0045] Example 2

[0046] This embodiment is substantially the same as Embodiment 1, except that the mass content of tris(dimethylamino)silyl trifluoromethanesulfonate in this embodiment is 0.3%.

[0047] Example 3

[0048] This embodiment is substantially the same as Embodiment 1, except that the mass content of tris(dimethylamino)silyl trifluoromethanesulfonate in this embodiment is 0.7%.

[0049] Example 4

[0050] This embodiment is substantially the same as Embodiment 1, except that the mass content of tris(dimethylamino)silyl trifluoromethanesulfonate in this embodiment is 0.5%.

[0051] Example 5

[0052] This embodiment is basically the same as Embodiment 1, except that LiPF6 is replaced by LiBF4 in this embodiment.

[0053] Example 6

[0054] This embodiment is basically the same as Embodiment 1, except that in this embodiment, LiPF6 is replaced by lithium borate oxalate (C4BLiO8).

[0055] Example 7

[0056] This embodiment is substantially the same as Embodiment 1, except that the mass content of LiPF6 in this embodiment is 10%.

[0057] Example 8

[0058] This embodiment is substantially the same as Embodiment 1, except that the mass content of LiPF6 in this embodiment is 15%.

[0059] Example 9

[0060] This embodiment is substantially the same as Embodiment 1, except that the mass ratio of dimethyl carbonate, ethyl methyl carbonate, ethylene carbonate and propylene carbonate in this embodiment is 40:25:25:5.

[0061] Example 10

[0062] This embodiment is substantially the same as Embodiment 1, except that the mass ratio of dimethyl carbonate, ethyl methyl carbonate, ethylene carbonate and propylene carbonate in this embodiment is 50:20:20:10.

[0063] Embodiment 11

[0064] This embodiment is substantially the same as Embodiment 2, except that no diethyl sulfate (DTD) is added in this embodiment.

[0065] Example 12

[0066] This embodiment is substantially the same as Embodiment 2, except that vinylene carbonate (VC) is not added in this embodiment.

[0067] Example 13

[0068] This embodiment is substantially the same as Embodiment 2, except that vinylene carbonate (VC) and diethyl sulfate (DTD) are not added in this embodiment.

[0069] Embodiment 14

[0070] This embodiment is substantially the same as Embodiment 1, except that the mass content of tris(dimethylamino)silyl trifluoromethanesulfonate in this embodiment is 2%.

[0071] Embodiment 15

[0072] This embodiment is substantially the same as Embodiment 1, except that the mass content of tris(dimethylamino)silyl trifluoromethanesulfonate in this embodiment is 15%.

[0073] Comparative Example 1

[0074] This comparative example is substantially the same as Example 13, except that tris(dimethylamino)silyl trifluoromethanesulfonate is not added in this comparative example.

[0075] Comparative Example 2

[0076] This comparative example is substantially the same as Example 13, except that in this comparative example, tris(dimethylamino)silyl trifluoromethanesulfonate is replaced by (trifluoromethyl)trimethylsilane.

[0077] Comparative Example 3

[0078] This comparative example is substantially the same as Example 13, except that in this comparative example, tris(dimethylamino)silyl trifluoromethanesulfonate is replaced by tris(dimethylamino)methylsilane.

[0079] Test example:

[0080] Battery discharge DC impedance (DCR) detection: The electrolyte samples prepared in the examples and comparative examples were injected into the LiMn 0.4 Fe 0.6 In the PO4 system lithium-ion battery, the DC internal resistance (DCR) at 25°C is tested. After adjusting the state of charge SOC to 50%, it is left for 1 hour, and the terminal voltage is recorded as V0. Discharge at a constant current of 1.0C for 60 seconds, and the terminal voltage is V1. Discharge: DCR = (V0-V1) / I, and the DCR of 50% SOC is calculated, as shown in Table 1.

[0081] Battery 25℃, 45℃ charge and discharge cycle test: The electrolyte samples prepared in the embodiment and the comparative example were injected into the LiMn 0.4 Fe 0.6In the PO4 lithium-ion battery, the charge and discharge are carried out at 0.5C at 25°C and 45°C, respectively, and the voltage range is 2.5-3.65V. The capacity retention rate is calculated as follows: capacity retention rate = 1000-week discharge capacity / first-week discharge capacity*100%, as shown in Table 1.

[0082] Data Sheet

[0083] Table 1 Test results of embodiments and comparative examples

[0084]

[0085]

[0086] As can be seen from Table 1, compared with Example 11, Example 12, and Example 13, the DC impedance of the lithium ion battery of Example 1 is lower and the capacity retention rate is higher. It can be seen that the use of vinylene carbonate (VC) and vinyl sulfate (DTD) as film-forming protective agents can improve the cycle performance of the battery. Compared with Example 14 and Example 15, the DC impedance of the lithium ion battery of Example 1-4 is lower and the capacity retention rate is higher. It can be seen that the amount of tris(dimethylamino)silyl trifluoromethanesulfonate added can affect the cycle performance of the battery. Compared with Comparative Example 1, the DC impedance of the lithium ion battery of the embodiment is lower and the capacity retention rate is higher. It can be seen that tris(dimethylamino)silyl trifluoromethanesulfonate can improve the cycle performance of the battery. Compared with Comparative Example 2 and Comparative Example 3, the DC impedance of the lithium ion battery of the embodiment is lower and the capacity retention rate is higher. It can be seen that tris(dimethylamino)silyl trifluoromethanesulfonate can improve the cycle performance of the battery compared to (trifluoromethyl)trimethylsilane and tris(dimethylamino)methylsilane.

[0087] The embodiments of the present invention are described in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. An electrolyte, characterized in that: The invention comprises a lithium salt, an organic solvent and an additive, wherein the functional group of the additive comprises a silicon group, a fluorine-containing alkyl group, an amino group and a sulfonate group.

2. The electrolyte according to claim 1, characterized in that The additive is tris(dimethylamino)silyl trifluoromethanesulfonate; and / or The lithium salt is at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium difluorophosphate, lithium difluorooxalatephosphate, and lithium dioxalateborate.

3. The electrolyte according to claim 1, characterized in that The mass content of the lithium salt in the electrolyte is 10-15%; and / or The mass content of the additive in the electrolyte is 0.3-1.0%.

4. The electrolyte according to claim 2, characterized in that The organic solvent includes dimethyl carbonate, ethyl methyl carbonate, ethylene carbonate and propylene carbonate, and the mass ratio of the dimethyl carbonate, the ethyl methyl carbonate, the ethylene carbonate and the propylene carbonate is (30-50):(20-30):(20-30):(1-10).

5. The electrolyte according to claim 2, characterized in that The electrolyte also includes a film-forming protective agent.

6. The electrolyte according to claim 5, characterized in that The mass content of the film-forming protective agent in the electrolyte is 2-4%; and / or The film-forming protective agent includes at least one of vinylene trithiocarbonate, vinyl sulfate, vinyl carbonate, vinylene carbonate, and fluoroethylene carbonate.

7. The electrolyte according to claim 5, characterized in that The film-forming protective agent includes vinylene carbonate and vinyl sulfate.

8. The electrolyte according to claim 7, characterized in that The mass ratio of vinylene carbonate to vinyl sulfate is (4-6):(1-2).

9. A battery, characterized in that: Comprising the electrolyte as described in any one of claims 1-8.

10. The battery according to claim 9, characterized in that The battery comprises a positive electrode, the chemical formula of the active material of the positive electrode is LiMn x Fe 1-x PO4, where 0<x<1.

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