Lithium ion battery electrolyte and application thereof

Abstract

The application provides a lithium ion battery electrolyte and application thereof, and the electrolyte comprises at least the following components: a lithium salt, a solvent and an additive, wherein the additive comprises a first additive and a second additive, the structural general formula of the first additive is: wherein R1 and R2 are each independently selected from one of H, a first substituted or unsubstituted C1-6 alkyl, a second substituted or unsubstituted C2-6 alkenyl and a third substituted or unsubstituted C3-6 cycloalkyl, the first, second and third substituents are each independently selected from an alkyl or a halogen atom, and the second additive comprises a cyclic sulfate. The lithium ion battery electrolyte and application thereof can improve the high-temperature cycle performance of the battery and reduce the impedance of the battery.

Description

Technical Field

[0001] This invention relates to the field of power battery technology, specifically to a lithium-ion battery electrolyte and its application. Background Technology

[0002] Facing the global energy transition and carbon neutrality goals, lithium-ion batteries are developing towards higher energy density, longer lifespan, lower cost, and greater safety. To extend battery life, various additives are added to the electrolyte to improve high-temperature cycle performance. However, while additives can improve high-temperature cycle performance, they can also lead to higher battery impedance, thus limiting further development and application. Summary of the Invention

[0003] This invention proposes a lithium-ion battery electrolyte and its application. The lithium-ion battery electrolyte and its application provided by this invention can improve the high-temperature cycle performance of the battery while reducing the battery impedance.

[0004] To address the aforementioned technical problems, the present invention provides a lithium-ion battery electrolyte, comprising at least the following components:

[0005] Lithium salts;

[0006] Solvent; and

[0007] The additives include a first additive and a second additive, wherein the first additive has the following general structural formula: R1 and R2 are each independently selected from H, a C1-6 alkyl group substituted or unsubstituted with a first substituent, a C2-6 alkenyl group substituted or unsubstituted with a second substituent, and a C3-6 cycloalkyl group substituted or unsubstituted with a third substituent, wherein the first substituent, the second substituent, and the third substituent are each independently selected from alkyl or halogen atoms, and the second additive comprises a cyclic sulfate ester.

[0008] In one embodiment of the present invention, the content of the first additive in the electrolyte is 0.1wt%-3.0wt%.

[0009] In one embodiment of the present invention, the cyclic sulfate is selected from at least one of vinyl sulfate or propylene sulfate, and the content of the cyclic sulfate in the electrolyte is 0.3wt%-4.0wt%.

[0010] In one embodiment of the present invention, the solvent comprises chain carbonates and cyclic carbonates, wherein the mass ratio of the chain carbonates to the cyclic carbonates is (1.5-4):1.

[0011] In one embodiment of the present invention, the cyclic carbonate is selected from at least one of ethylene carbonate or propylene carbonate.

[0012] In one embodiment of the present invention, the chain carbonate is selected from at least one of dimethyl carbonate, ethyl methyl carbonate, or diethyl carbonate.

[0013] In one embodiment of the present invention, the lithium salt is selected from at least one of lithium hexafluorophosphate or lithium bisfluorosulfonylimide.

[0014] In one embodiment of the present invention, the lithium salt includes lithium hexafluorophosphate and lithium difluorosulfonylimide, and the mass ratio of lithium hexafluorophosphate to lithium difluorosulfonylimide is (0.5-2):1.

[0015] In one embodiment of the present invention, the additive further includes a third additive, which includes hexamethylene diisocyanate, and the content of the third additive in the electrolyte is 0.3wt%-0.5wt%.

[0016] The present invention also provides a lithium-ion battery, comprising at least:

[0017] The positive electrode includes a positive electrode active material, wherein the positive electrode active material is selected from at least one of lithium iron phosphate, lithium nickel manganese oxide, lithium-rich manganese-based materials, lithium manganese iron phosphate, lithium cobalt oxide, or lithium nickel cobalt manganese oxide ternary materials.

[0018] A negative electrode includes a negative electrode active material, said negative electrode active material being selected from at least one of graphite, silicon, or silicon oxides;

[0019] A diaphragm is disposed between the positive electrode and the negative electrode; and

[0020] The electrolyte is selected from the lithium-ion battery electrolytes mentioned above.

[0021] In summary, this invention proposes a lithium-ion battery electrolyte and its application. The first and second additives work synergistically to form a network-like solid electrolyte interface (SEI) film, effectively protecting the positive and negative electrodes and thus improving the battery's high-temperature cycle performance. Furthermore, the SEI film provides abundant lithium-ion channels, thereby reducing the battery's impedance. The third additive further significantly improves the battery's high-temperature cycle performance while further reducing its impedance. Detailed Implementation

[0022] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0023] It should be understood that the invention can be embodied in various forms and should not be construed as being limited to the embodiments set forth herein. Rather, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0024] The technical solution of the present invention will be further described in detail below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] This invention proposes a lithium-ion battery electrolyte, comprising at least a lithium salt, a solvent, and additives, wherein the additives include a first additive and a second additive, and the first additive has the following general structural formula: Formula 1; wherein R1 and R2 are each independently selected from one of H, a first substituent-substituted or unsubstituted alkyl group, a second substituent-substituted or unsubstituted alkenyl group, and a third substituent-substituted or unsubstituted cycloalkyl group, etc., and the first substituent, second substituent, and third substituent are each independently selected from alkyl or halogen atoms, etc., and the second additive includes cyclic sulfate esters. In the lithium-ion battery electrolyte provided by the present invention, the first additive and the second additive work synergistically to improve the high-temperature cycle performance of the battery while reducing the impedance of the SEI film.

[0026] In one embodiment of the present invention, in Formula 1, the structures of R1 and R2 can be the same or different. Further, in this embodiment, R1 is, for example, H, and R2 is, for example, methyl, i.e., the first additive is, for example, H. Compound 1. The content of the first additive in the electrolyte is, for example, 0.1 wt%-3.0 wt%, and further, for example, 0.3 wt%-1 wt%. By controlling the content of the first additive, both the high-temperature cycle performance and impedance of the battery can be considered.

[0027] In one embodiment of the present invention, the cyclic sulfate ester in the second additive is selected from at least one of ethylene sulfate (DTD) or propylene sulfate (ES). In this embodiment, taking DTD as the second additive as an example, the synergistic effect of the first and second additives is explained. Specifically, under acidic conditions, the CO bond in DTD breaks, the C at the breakage site forms a carbocation, and the O at the breakage site forms an oxygen anion. The oxygen anion attacks the unsaturated CH group at one end of the carbon-carbon double bond in Formula 1, causing the unsaturated bond in Formula 1 to break and polymerize, forming an SEI film. Meanwhile, the carbocation attacks the C in C=O in Formula 1, forming a network-like SEI film, thereby effectively protecting the positive and negative electrodes and improving the high-temperature cycle performance of the battery. Furthermore, the SEI film can also provide abundant lithium-ion shuttle channels, thereby effectively reducing impedance.

[0028] In one embodiment of the present invention, the additive further includes a third additive, which comprises hexamethylene diisocyanate (HDI), and the content of the third additive in the electrolyte is, for example, 0.3wt%-0.5wt%. By introducing the third additive, the high-temperature cycle performance of the battery can be significantly improved while the impedance can be further reduced. Moreover, by controlling the content of the third additive, both the high-temperature cycle performance and impedance of the battery can be balanced.

[0029] In one embodiment of the present invention, the solvent includes cyclic carbonates and chain carbonates, wherein the cyclic carbonate is selected from at least one of ethylene carbonate (EC) or propylene carbonate (PC), and the chain carbonate is selected from at least one of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), or diethyl carbonate (DEC), and the mass ratio of chain carbonate to cyclic carbonate is, for example, (1.5-4):1. By controlling the ratio of cyclic carbonate to chain carbonate, the electrolyte performance is maximized while preventing excessive solvent content, which could lead to excessive electrolyte viscosity and consequently reduced ionic conductivity and wettability of the electrolyte.

[0030] In one embodiment of the present invention, the lithium salt is selected from at least one of lithium hexafluorophosphate (LiPF6) or lithium bisfluorosulfonylimide (LiFSI), and the content of the lithium salt in the electrolyte is, for example, 10wt%-18wt%. Specifically, in this embodiment, the lithium salt includes, for example, LiPF6 and LiFSI, and the mass ratio of LiPF6 to LiFSI is, for example, (0.5-2):1. By controlling the mass ratio of LiPF6 to LiFSI, both the high-temperature cycle performance and impedance of the battery can be balanced.

[0031] In one embodiment of the present invention, when preparing the electrolyte, cyclic carbonate and chain carbonate are mixed evenly in a glove box under a stable gas atmosphere such as argon at a mass ratio to obtain a solvent. Lithium salt, a first additive, a second additive, and a third additive are then added to the solvent and mixed evenly to prepare a lithium-ion battery electrolyte. The moisture content in the glove box is, for example, less than 10 ppm.

[0032] This invention also proposes a lithium-ion battery, comprising a positive electrode, a separator, a negative electrode, and an electrolyte. The separator is located between the positive and negative electrodes to prevent short circuits between them, allowing lithium ions to pass through. The electrolyte fills the space between the positive electrode, the separator, and the negative electrode, and is the aforementioned lithium-ion battery electrolyte, serving to conduct ions. The lithium-ion battery can be, for example, a primary battery or a secondary battery. A secondary battery can be, for example, a pouch battery, a hard-case battery, or a cylindrical battery. This invention does not specifically limit the type or category of lithium-ion batteries.

[0033] In one embodiment of the present invention, the positive electrode includes a positive electrode current collector and a positive electrode active layer coated on at least one surface of the positive electrode current collector. The positive electrode current collector is, for example, a foil formed by surface treatment of materials such as nickel, titanium, aluminum, silver, stainless steel, or carbon. Besides foil, the positive electrode current collector can also be used in any one or more combinations of various forms such as film, mesh, porous, foam, or nonwoven fabric.

[0034] In one embodiment of the present invention, the positive electrode active layer includes a positive electrode active material, a conductive agent, and a binder. The ratio of the positive electrode active material, the conductive agent, and the binder can be selected according to actual needs. In this embodiment, the positive electrode active material is selected from at least one of lithium iron phosphate, lithium nickel manganese oxide, lithium-rich manganese-based materials, lithium manganese iron phosphate, lithium cobalt oxide, or lithium nickel cobalt manganese oxide ternary materials. The chemical formula of the lithium nickel cobalt manganese oxide ternary material is, for example, LiNi. x Co y Mn z O2, x+y+z=1.

[0035] In one embodiment of the present invention, the conductive agent is selected from at least one of conductive carbon black (Super P), acetylene black, carbon nanotubes, or graphene, and the binder is selected from at least one of polyvinylidene fluoride (PVDF), poly(ethylene oxide) (PEO), polyamide (PA), polyacrylonitrile (PAN), polyacrylate (polyacrylate), polyvinyl ether (polyvinyl ether), polymethyl methacrylate (PMMA), ethylene-propylene-diene terpolymer (EPDM), polyhexanefluoropropylene (polyhexafluoropropylene), or polymerized styrene-butadiene rubber (SBR).

[0036] In one embodiment of the present invention, the positive electrode current collector is, for example, aluminum foil; the positive electrode active material is, for example, lithium iron phosphate; the conductive agent is, for example, acetylene black; and the binder is, for example, PVDF. The positive electrode active material, conductive agent, and binder are mixed in a mass ratio of, for example, 95:3:2, dissolved in an organic solvent, and stirred under vacuum until the system is homogeneous to obtain a positive electrode slurry. The positive electrode slurry is then uniformly coated onto the aluminum foil, air-dried at room temperature, and then transferred to an oven for drying. The positive electrode is obtained through processes such as rolling and cutting. The organic solvent is, for example, N-methylpyrrolidone (NMP).

[0037] In one embodiment of the present invention, the negative electrode includes, for example, a negative electrode current collector and a negative electrode active layer coated on at least one surface of the negative electrode current collector. The negative electrode current collector is selected, for example, from a copper foil current collector, a composite copper foil current collector, a carbon current collector, a foamed copper current collector, or a stainless steel current collector.

[0038] In one embodiment of the present invention, the negative electrode active layer includes a negative electrode active material, a conductive agent, and a binder. The ratio of the negative electrode active material, the conductive agent, and the binder can be selected according to actual needs. In this embodiment, the negative electrode active material is selected from at least one of graphite, silicon, or silicon oxide compounds. Further, the negative electrode active material is, for example, selected from at least one of artificial graphite, natural graphite, soft carbon, hard carbon, pure silicon, silicon oxide compounds, and silicon carbide compounds.

[0039] In one embodiment of the present invention, the binder is selected from at least one of PVDF, PEO, PA, polypropylene, polyacrylate, polyethylene ether, PMMA, sodium carboxymethyl cellulose (CMC), polyhexamethylene propylene, or SBR. The conductive agent is selected from at least one of conductive carbon black, acetylene black, Ketjen black, carbon nanotubes, or graphene.

[0040] In one embodiment of the present invention, the negative electrode current collector is, for example, copper foil, the negative electrode active material is, for example, silicon suboxide, the conductive agent is, for example, acetylene black, and the binder is, for example, CMC. Specifically, the negative electrode active material, conductive agent, and binder carbon are mixed in a mass ratio of 96:2:2, and deionized water solvent is added. The mixture is then thoroughly stirred and homogenized under the action of a vacuum mixer to obtain a negative electrode slurry. The negative electrode slurry is coated onto copper foil, and after being air-dried at room temperature, it is transferred to an oven for drying. After processes such as rolling and cutting, the negative electrode is obtained.

[0041] In one embodiment of the present invention, the separator is, for example, a conventional separator, a ceramic separator, a polymer separator, a non-woven fabric separator, or an inorganic-organic composite separator. Specifically, the separator is, for example, a single-layer polypropylene (PP) membrane, a single-layer polyethylene (PE) membrane, a double-layer PP / PE membrane, a double-layer PP / PP membrane, or a triple-layer PP / PE / PP membrane. In this embodiment, a single-layer PP membrane is selected as the separator, for example.

[0042] In one embodiment of the present invention, the above-mentioned positive electrode, separator and negative electrode are placed in sequence, so that the separator is in the middle of the positive electrode and the negative electrode to play a role in isolation, and is put into an aluminum-plastic film to obtain a dry cell. Then, the dry cell is baked at 80°C to remove water, the electrolyte is injected into the dry cell and sealed to obtain a lithium-ion battery.

[0043] The present invention will be explained in more detail below by referring to embodiments, which should not be construed as limiting. Appropriate modifications can be made within the scope of the present invention, and all such modifications fall within the technical scope of the present invention.

[0044] Example 1

[0045] Preparation of the positive electrode: Lithium iron phosphate, acetylene black and PVDF are mixed in a mass ratio of 95:3:2, dissolved in NMP organic solvent, and stirred in a vacuum mixer until the system is homogeneous to obtain the positive electrode slurry. The positive electrode slurry is then uniformly coated on aluminum foil, dried at room temperature and then transferred to an oven for drying. The positive electrode is obtained through processes such as rolling and cutting.

[0046] Preparation of the negative electrode: Silicon suboxide, acetylene black and CMC are mixed in a mass ratio of 96:2:2, and deionized water solvent is added. The mixture is then stirred and mixed thoroughly under vacuum to obtain a negative electrode slurry. The negative electrode slurry is coated onto copper foil, and then dried at room temperature before being transferred to an oven for drying. After rolling and cutting, the negative electrode is obtained.

[0047] Electrolyte preparation: In an argon-atmospheric glove box with a moisture content of less than 1 ppm, EC, EMC, and DEC were mixed uniformly at a mass ratio of 3:5:2 according to the electrolyte composition described in Table 1 to obtain a solvent. LiPF6, LiFSI, Compound 1, and DTD were then added to the solvent and mixed uniformly to prepare the lithium-ion battery electrolyte. The contents of LiPF6, LiFSI, Compound 1, and DTD in the electrolyte were 10 wt%, 5 wt%, 0.1 wt%, and 0.5 wt%, respectively.

[0048] Selection of diaphragm: Single-layer PP membrane is selected as the diaphragm.

[0049] Battery preparation: The positive electrode, separator and negative electrode are placed in sequence and put into an aluminum-plastic film to obtain a dry cell. Then, the dry cell is baked at 80°C to remove water. Electrolyte is injected into the dry cell and it is then packaged to obtain a lithium-ion battery.

[0050] Example 2

[0051] The content of compound 1 in the electrolyte was 0.3 wt%, and the other steps were the same as in Example 1.

[0052] Example 3

[0053] The content of compound 1 in the electrolyte is 0.5 wt%, and the other steps are the same as in Example 1.

[0054] Example 4

[0055] The content of compound 1 in the electrolyte is 1 wt%, and the other steps are the same as in Example 1.

[0056] Example 5

[0057] The content of compound 1 in the electrolyte is 3 wt%, and the other steps are the same as in Example 1.

[0058] Example 6

[0059] The DTD content in the electrolyte is 0.3 wt%, and the other steps are the same as in Example 3.

[0060] Example 7

[0061] The DTD content in the electrolyte is 1 wt%, and the other steps are the same as in Example 3.

[0062] Example 8

[0063] The DTD content in the electrolyte is 2 wt%, and the other steps are the same as in Example 3.

[0064] Example 9

[0065] The DTD content in the electrolyte is 4 wt%, and the other steps are the same as in Example 3.

[0066] Example 10

[0067] The electrolyte also contains HDI, and the content of HDI in the electrolyte is 0.5 wt%. The other steps are the same as in Example 8.

[0068] Example 11

[0069] The HDI content in the electrolyte is 0.3 wt%, and the other steps are the same as in Example 10.

[0070] Example 12

[0071] The contents of LiPF6 and LiFSI in the electrolyte are 7.5 wt% and 7.5 wt%, respectively, and the other steps are the same as in Example 8.

[0072] Example 13

[0073] The contents of LiPF6 and LiFSI in the electrolyte are 5wt% and 10wt%, respectively, and the other steps are the same as in Example 8.

[0074] Example 14

[0075] The contents of EC, EMC and DEC in the total solvent are 40wt%, 45wt% and 15wt%, respectively, and the other steps are the same as in Example 8.

[0076] Example 15

[0077] The contents of EC, EMC and DEC in the total solvent are 20wt%, 55wt% and 25wt%, respectively, and the other steps are the same as in Example 8.

[0078] Comparative Example 1

[0079] The DTD content in the electrolyte is 0, and the other steps are the same as in Example 3.

[0080] Comparative Example 2

[0081] The content of compound 1 in the electrolyte was 0, and the other steps were the same as in Example 8.

[0082] Comparative Example 3

[0083] The content of compound 1 in the electrolyte was 0, and the other steps were the same as those in Comparative Example 1.

[0084] The content and mass ratio of raw material components required for the electrolytes prepared in each embodiment and comparative example are shown in Table 1. The content of each component is a mass percentage calculated based on the total mass of the electrolyte.

[0085] Table 1. Composition of electrolytes in Examples 1-15 and Comparative Examples 1-3

[0086]

[0087] In this invention, the lithium-ion batteries prepared with different electrolyte ratios in Examples 1-15 and Comparative Examples 1-3 were subjected to performance tests, and the test results are shown in Table 2.

[0088] In one embodiment of the present invention, a high-temperature cycle performance test is performed on a lithium-ion battery, for example. Specifically, at 45°C, the lithium-ion battery is charged at a constant current of 1 / 3C to 3.8V, and then charged at a constant voltage to a current of 0.05C. The battery is then discharged at a constant current of 1 / 3C to 2.0V, and the battery capacity C0 is recorded. The above charge-discharge steps are repeated 1000 times, and the battery discharge capacity C1 after 1000 cycles is recorded. The battery capacity retention rate is calculated according to the following formula:

[0089] Capacity retention rate = C1 / C0 100%.

[0090] In one embodiment of the present invention, for example, a direct current resistance (DCR) test is performed on a lithium-ion battery. Specifically, at 25°C, an uncycled lithium-ion battery is charged at a constant current of 1 / 3C to 4.25V, and then charged at a constant voltage to a current of 0.05C. The battery is then discharged at a constant current of 1 / 3C to 2.5V. The above charging steps are repeated, and the charging capacity is recorded as C1. The battery is then discharged at a constant current of 1 / 3C to (50%). C1), record the initial voltage as V2. Discharge the battery at a constant current of 1C for 30s, and record the final voltage as V3. Calculate DCR according to the following formula:

[0091] DCR=(V2-V3) / (C1 1).

[0092] Table 2 shows the performance test results of lithium-ion batteries in Examples 1-15 and Comparative Examples 1-3.

[0093]

[0094] Please refer to Tables 1 and 2. By comparing Comparative Example 1 and Comparative Example 3, it can be seen that when the electrolyte contains Compound 1, the battery capacity retention rate increases, but the impedance also increases. This indicates that although the introduction of Compound 1 can improve the high-temperature cycle performance of the battery, it also leads to the degradation of the battery impedance.

[0095] Please refer to Tables 1 and 2. By comparing Comparative Example 1 and Comparative Example 2, it can be seen that when the electrolyte contains DTD, the battery capacity retention rate increases, but the impedance also increases. This indicates that although the introduction of DTD can improve the high-temperature cycle performance of the battery, it also leads to the degradation of the battery impedance.

[0096] Please refer to Tables 1 and 2. Comparing Example 9 and Comparative Examples 1-3, it can be seen that when the electrolyte contains both Compound 1 and DTD, the battery capacity retention rate significantly increases and the impedance decreases. This indicates that Compound 1 and DTD work synergistically to form a network-like SEI film, effectively protecting the positive and negative electrodes, thereby significantly improving the battery's high-temperature cycling performance. Simultaneously, the SEI film also provides abundant lithium-ion channels, effectively reducing impedance. Therefore, the synergistic effect of Compound 1 and DTD can improve the battery's high-temperature cycling performance while reducing its impedance.

[0097] Please refer to Tables 1 and 2. Comparing Examples 1-5, it can be seen that as the content of Compound 1 increases, the impedance gradually increases, while the capacity initially increases and then decreases. That is, the high-temperature cycle performance of the battery shows a trend of first increasing and then decreasing. This indicates that by controlling the content of Compound 1, it is possible to balance the high-temperature cycle performance and impedance of the battery.

[0098] Please refer to Tables 1 and 2. Comparing Examples 6-9, it can be seen that as the DTD content increases, the impedance gradually increases, while the capacity initially increases and then decreases. That is, the high-temperature cycle performance of the battery shows a trend of first increasing and then decreasing. This indicates that by controlling the DTD content, it is possible to balance the high-temperature cycle performance and impedance of the battery.

[0099] Please refer to Tables 1 and 2. By comparing Example 8 and Example 10, it can be seen that when the electrolyte contains HDI, the battery capacity retention rate increases and the impedance decreases, thus indicating that HDI can further improve the high-temperature cycle performance of the battery while further reducing the battery impedance.

[0100] Please refer to Tables 1 and 2. Comparing Examples 10-11, it can be seen that as the HDI content increases, although the battery impedance increases, the capacity retention also increases. This indicates that although the battery impedance is affected by the increase in HDI content, the high-temperature cycle performance of the battery is improved. Therefore, by controlling the HDI content, it is possible to balance the high-temperature cycle performance and impedance of the battery.

[0101] Please refer to Tables 1 and 2. Comparing Examples 8 and 12-13, it can be seen that as the mass ratio of LiPF6 to LiFSI increases, although the battery impedance increases, the capacity retention also increases. This indicates that while the battery impedance is somewhat affected by increasing the mass ratio of LiPF6 to LiFSI, the high-temperature cycling performance of the battery is improved. Therefore, by controlling the mass ratio of LiPF6 to LiFSI, it is possible to balance the high-temperature cycling performance and impedance of the battery.

[0102] Please refer to Tables 1 and 2. Comparing Examples 8 and 14-15, it can be seen that as the mass ratio of chain carbonates (EMC and DMC) and cyclic carbonates (EC) increases, although the battery capacity retention decreases, the impedance also decreases. This indicates that while the high-temperature cycle performance of the battery is affected by increasing the mass ratio of chain carbonates to cyclic carbonates, the battery impedance is improved. Therefore, by controlling the mass ratio of chain carbonates to cyclic carbonates, it is possible to balance the high-temperature cycle performance and impedance of the battery.

[0103] This invention also provides an electronic device comprising at least one of the aforementioned lithium-ion batteries, which provides electrical energy. The electronic device can be a vehicle, mobile phone, portable device, laptop computer, ship, spacecraft, electric toy, or power tool, etc. In one embodiment of this invention, the vehicle is, for example, a new energy vehicle, which can be a pure electric vehicle, a hybrid electric vehicle, or a range-extended electric vehicle, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. The electronic device includes the aforementioned lithium-ion battery, and therefore the advantages of including the aforementioned lithium-ion battery are not elaborated here.

[0104] In summary, this invention proposes a lithium-ion battery electrolyte and its application. By introducing a first additive and a second additive into the electrolyte, the first and second additives work synergistically to form a network-like SEI film, effectively protecting the positive and negative electrodes, thereby improving the high-temperature cycle performance of the battery. Furthermore, the SEI film provides abundant lithium-ion channels, thus reducing impedance. By introducing a third additive into the electrolyte, the high-temperature cycle performance of the battery can be further improved while the impedance is further reduced, thereby optimizing the battery performance.

[0105] The above description is merely a preferred embodiment of this application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to the technical solutions formed by a specific combination of the above-mentioned technical features, but should also cover other technical solutions formed by any combination of the above-mentioned technical features or their equivalent features without departing from the inventive concept. For example, technical solutions formed by replacing the above-mentioned features with technical features with similar functions disclosed in this application (but not limited to) each other.

[0106] Apart from the technical features described in the specification, the other technical features are known to those skilled in the art. To highlight the innovative features of this invention, the other technical features will not be described in detail here.

Claims

1. A lithium-ion battery electrolyte, characterized in that, It includes at least the following components: Lithium salts; Solvent; as well as The additives include a first additive, a second additive, and a third additive, wherein the first additive is: The second additive includes a cyclic sulfate, and the content of the cyclic sulfate in the electrolyte is 0.3wt%-4.0wt%, and the third additive includes hexamethylene diisocyanate.

2. The lithium-ion battery electrolyte according to claim 1, characterized in that, The content of the first additive in the electrolyte is 0.1wt%-3.0wt%.

3. The lithium-ion battery electrolyte according to claim 1, characterized in that, The cyclic sulfate is selected from at least one of vinyl sulfate or propylene sulfate.

4. The lithium-ion battery electrolyte according to claim 1, characterized in that, The solvent includes chain carbonates and cyclic carbonates, wherein the mass ratio of the chain carbonates to the cyclic carbonates is (1.5-4):

1.

5. The lithium-ion battery electrolyte according to claim 4, characterized in that, The cyclic carbonate is selected from at least one of ethylene carbonate or propylene carbonate.

6. The lithium-ion battery electrolyte according to claim 4, characterized in that, The chain carbonate is selected from at least one of dimethyl carbonate, ethyl methyl carbonate, or diethyl carbonate.

7. The lithium-ion battery electrolyte according to claim 1, characterized in that, The lithium salt is selected from at least one of lithium hexafluorophosphate or lithium bis(fluorosulfonyl)imide.

8. The lithium-ion battery electrolyte according to claim 7, characterized in that, The lithium salt comprises lithium hexafluorophosphate and lithium difluorosulfonylimide, and the mass ratio of lithium hexafluorophosphate to lithium difluorosulfonylimide is (0.5-2):

1.

9. The lithium-ion battery electrolyte according to claim 1, characterized in that, The content of the third additive in the electrolyte is 0.3wt%-0.5wt%.

10. A lithium-ion battery, characterized in that, At least including: The positive electrode includes a positive electrode active material, wherein the positive electrode active material is selected from at least one of lithium iron phosphate, lithium nickel manganese oxide, lithium-rich manganese-based materials, lithium manganese iron phosphate, lithium cobalt oxide, or lithium nickel cobalt manganese oxide ternary materials. A negative electrode includes a negative electrode active material, said negative electrode active material being selected from at least one of graphite, silicon, or silicon oxides; A diaphragm is disposed between the positive electrode and the negative electrode; and The electrolyte is selected from the lithium-ion battery electrolyte according to any one of claims 1-9.

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