Electrolytes and lithium ion batteries

Abstract

The application relates to the technical field of lithium ion batteries, in particular to an electrolyte and a lithium ion battery. The electrolyte comprises an organic solvent, a lithium salt, a silane compound, a ring compound and lithium difluoro(oxalato)borate. The electrolyte effectively improves the performance and safety of the battery cell through the synergistic effect between the additives, and meanwhile, the long cycle and low swelling performance are considered. In the electrolyte, ethyl propionate and lithium bis(trifluoromethylsulfonyl)imide which is easier to dissociate are added, the solvent viscosity is reduced, the electrolyte wettability and ion conductivity are greatly improved, the low-temperature disadvantage caused by the thick SEI film with large impedance generated by the combination of the silane compound and the ring compound is improved, and the low-temperature performance of the battery cell is improved. Through the synergistic effect between the electrolyte and the negative electrode material, the lithium ion battery prepared by using the silicon-doped negative electrode material can effectively improve the safety performance of the battery cell, and meanwhile, the long cycle and low-temperature performance of the battery cell are considered.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery technology, specifically to electrolytes and lithium-ion batteries. Background Technology

[0002] In recent years, lithium-ion batteries have been widely used in smartphones, tablets, smart wearables, power tools, and electric vehicles. As the application of lithium-ion batteries becomes increasingly widespread, consumers' demands for the usage environment and performance of lithium-ion batteries are constantly rising. This requires lithium-ion batteries to have high safety while maintaining long lifespan and excellent performance at both high and low temperatures.

[0003] Currently, lithium-ion batteries pose safety hazards during use. For example, when batteries are subjected to extreme conditions such as sustained high temperatures, they are prone to serious safety accidents such as fires or even explosions. The main reasons for these problems include the structural instability of active materials under high temperatures and high voltages, and the violent reaction between the electrolyte and lithium graphite releasing a large amount of heat, causing the cell temperature to rise continuously and thus triggering thermal runaway.

[0004] To overcome the aforementioned technical problems, there is an urgent need to develop lithium-ion batteries with high safety and high voltage. Currently, the main approach to improving battery safety is to add flame retardants (such as trimethyl phosphate) to the electrolyte. However, the use of these flame retardant additives often leads to battery performance degradation and severely shortens cell lifespan. Therefore, developing lithium-ion batteries that simultaneously possess high safety and high voltage without compromising their electrochemical performance is a pressing technical challenge. Summary of the Invention

[0005] In view of this, the present invention provides an electrolyte and a lithium-ion battery. This high-voltage lithium-ion battery not only has excellent electrochemical performance and long lifespan, but also high safety.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides an electrolyte comprising an organic solvent, a lithium salt, a first additive, a second additive, and a third additive;

[0008] The first additive includes silane compounds;

[0009] The second additive includes bicyclic compounds;

[0010] The third additive includes lithium difluorooxalate borate.

[0011] Preferably, the first additive silane compound includes tetravinylsilane;

[0012] Preferably, the second additive dicyclic compound includes at least one of the compounds shown in formulas T1 to T8;

[0013]

[0014] Preferably, the amount of the first additive is 0.2wt% to 1wt% of the total mass of the electrolyte; for example, it is 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1wt%, or any range of the aforementioned values ​​and any point within the range.

[0015] Preferably, the amount of the second additive is 1 wt% to 5 wt% of the total mass of the electrolyte; for example, it is 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, or any range of the aforementioned values ​​and any point within the range.

[0016] Preferably, the amount of the third additive is 0.1wt% to 1wt% of the total mass of the electrolyte; for example, it is 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, or 1wt%, or any range of values ​​formed by any pair of the aforementioned values ​​and any point within the range.

[0017] In a specific embodiment provided by the present invention, the amount of the third additive is 0.13wt% to 1wt% of the total mass of the electrolyte.

[0018] Preferably, the amounts of the first additive and the second additive satisfy the following conditions:

[0019] 0.07≤C A / C B ≤0.8

[0020] Among them, C A C indicates the amount of the first additive added. B This indicates the amount of the second additive added.

[0021] More preferably, the amounts of the first additive and the second additive satisfy the following conditions:

[0022] 0.08≤C A / C B ≤0.77

[0023] Preferably, the organic solvent includes a first organic solvent, or includes both a first organic solvent and a second organic solvent;

[0024] The first organic solvent includes ethyl propionate;

[0025] The second organic solvent includes at least one of ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, propyl propionate (PP), and propyl acetate.

[0026] In a specific embodiment provided by the present invention, the second organic solvent includes ethylene carbonate (EC), propylene carbonate (PC), and propyl propionate (PP). The three solvents can be mixed in any mass ratio, exemplarily 1:1:1.

[0027] Preferably, the amount of the first organic solvent added accounts for 5 wt% to 70 wt% of the total mass of the electrolyte. Examples include 5 wt%, 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, and 70 wt%, or any range of values ​​formed by any pair of the aforementioned values ​​and any point within that range.

[0028] Preferably, the amount of the first organic solvent added accounts for 20wt% to 60wt% of the total mass of the electrolyte. Examples include 20wt%, 30wt%, 40wt%, 50wt%, and 60wt%, or any range of values ​​formed by any pair of the aforementioned values ​​and any point within that range.

[0029] More preferably, the amount of the first organic solvent added accounts for 20 to 50 wt% of the total mass of the electrolyte.

[0030] Preferably, the lithium salt includes lithium hexafluorophosphate and / or lithium bis(trifluoromethanesulfonyl)imide.

[0031] Preferably, the amount of lithium hexafluorophosphate added is 13wt% to 20wt% of the total mass of the electrolyte; for example, it is 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, 19wt%, 20wt%, or any range of the aforementioned values ​​and any point within the range.

[0032] Preferably, the amount of lithium bis(trifluoromethanesulfonyl)imide added is 0.5 wt% to 10 wt% of the total mass of the electrolyte. Examples include 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, and 10 wt%, or any range of the aforementioned values ​​and any point within that range.

[0033] Preferably, the electrolyte also includes a fourth additive and / or a fifth additive.

[0034] Preferably, the fourth additive includes at least one of tris(trimethylsilane) phosphite, tris(trimethylsilyl) borate, lithium difluorosulfonylimide, 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, vinyl sulfite, vinyl sulfate, vinylene carbonate, fluorovinyl carbonate, lithium dioxalate borate, lithium difluorooxalate phosphate, and vinyl ethylene carbonate.

[0035] Preferably, the amount of the fourth additive is 0 to 10 wt% of the total mass of the electrolyte; for example, it is 0.1 wt%, 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, or any range of the aforementioned values ​​and any point within that range.

[0036] Preferably, the fifth additive includes fluorinated substituted boron ether compounds;

[0037] Preferably, the fluorine-substituted boron ether compounds include at least one of the compounds shown in Formulas T9 to T11;

[0038]

[0039] Preferably, the amount of fluorinated substituted boron ether compound added accounts for 0.1 wt% to 1 wt% of the total mass of the electrolyte. Examples include 0.1 wt%, 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, and 10 wt%, or any range of the aforementioned values ​​and any point within that range.

[0040] The present invention also provides a lithium-ion battery, which includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and the electrolyte described above.

[0041] In this invention, the negative electrode active material of the negative electrode sheet contains silicon-based materials.

[0042] Preferably, the silicon-based material is selected from at least one of silicon, silicon-carbon, SiOx, and SiO2, wherein 0 <x<2。

[0043] As a preferred option, the negative electrode active material of the negative electrode sheet also includes carbon materials;

[0044] Preferably, the carbon material includes at least one of artificial graphite, natural graphite, mesophase carbon microspheres, hard carbon, and soft carbon.

[0045] In the specific embodiments provided by the present invention, the carbon material includes graphite material.

[0046] As a preferred option, the mass ratio of silicon-based material to carbon material is (1-40):(60-99).

[0047] Preferably, the mass ratio of silicon-based material to carbon material is (5-30):(70-95).

[0048] In specific embodiments provided by the present invention, the negative electrode active material of the negative electrode sheet includes a mixture of graphite and silicon carbon, or a mixture of graphite and SiO2.

[0049] In the embodiments provided by the present invention, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on at least one side of the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material, a conductive agent, and a binder.

[0050] Preferably, the mass percentage of each component in the negative electrode active material layer is: 70wt% to 99.7wt% of negative electrode active material, 0.1wt% to 10wt% of conductive agent, and 0.1wt% to 10wt% of binder.

[0051] In one exemplary embodiment provided by the present invention, the mixing mass ratio of the negative electrode active material, the conductive agent and the binder is 97.4:0.7:1.9.

[0052] Preferably, the positive electrode sheet includes a positive current collector and a positive active material layer coated on at least one side of the positive current collector, wherein the positive active material layer includes a positive active material, a conductive agent, and a binder.

[0053] Preferably, the mass percentage of each component in the positive electrode active material layer is: 70wt% to 99.7wt% of positive electrode active material, 0.1wt% to 10wt% of conductive agent, and 0.1wt% to 10wt% of binder.

[0054] In one exemplary embodiment of the present invention, the mass ratio of the positive electrode active material, the conductive agent and the binder is 97.6:1.1:1.3.

[0055] Preferably, the positive electrode active material is selected from lithium cobalt oxide (LiCoO2) or lithium cobalt oxide (LiCoO2) doped with two, three or more elements selected from Al, Mg, Mn, Cr, Ti, and Zr. The chemical formula of the lithium cobalt oxide doped with two, three or more elements selected from Al, Mg, Mn, Cr, Ti, and Zr is Li. x Co 1-y1-y2-y3-y4 A y1 B y2 C y3 D y4O2; 0.95≤x≤1.05, 0.01≤y1≤0.1, 0.01≤y2≤0.1, 0≤y3≤0.1, 0≤y4≤0.1, A, B, C, and D are independently selected from two, three, or more elements from Al, Mg, Mn, Cr, Ti, and Zr.

[0056] Preferably, the median particle size D of lithium cobalt oxide treated with doping of two, three or more elements selected from Al, Mg, Mn, Cr, Ti, and Zr is [not specified]. 50 Its thickness is 10–17 μm, and its specific surface area (BET) is 0.15–0.45 m². 2 / g.

[0057] Preferably, the conductive agent includes at least one of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, carbon nanotubes, metal powder, and carbon fiber.

[0058] Preferably, the binder includes at least one of polyvinylidene fluoride (PVDF), ethylene, styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), polytetrafluoroethylene, and polyethylene oxide.

[0059] In a specific embodiment of the present invention, the conductive agent in the positive electrode active material layer includes acetylene black.

[0060] In a specific embodiment of the present invention, the binder in the positive electrode active material layer includes polyvinylidene fluoride (PVDF).

[0061] In a specific embodiment of the present invention, the conductive agent in the negative electrode active material layer includes conductive carbon black and carbon nanotubes.

[0062] In a specific embodiment of the present invention, the binder in the negative electrode active material layer includes styrene-butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC).

[0063] Preferably, the lithium-ion battery is a high-voltage lithium-ion battery.

[0064] Preferably, the charging cut-off voltage of the lithium-ion battery is 4.5V or higher.

[0065] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0066] (1) In this invention, the electrolyte effectively improves the cell performance and safety performance through the synergistic effect between additives, while also taking into account long cycle life and low expansion performance. The first additive, tetravinylsilane, and the second additive, a cyclic compound, are used together. When the amount of the two substances added is in a certain proportion, they can cross-link on the negative electrode surface to form a thicker and more stable SEI protective film, so as to prevent the electrolyte from being reduced on the negative electrode surface, thereby reducing the exothermic side reaction and improving the problem of increased cycle expansion caused by silicon-based negative electrode, so as to improve the safety performance and long cycle life of the battery.

[0067] The introduction of a third additive, lithium difluorooxalate borate, allows the three substances to be used together to form a more resilient composite protective film on the negative electrode, thereby enhancing the safety performance of the battery cell.

[0068] Furthermore, a fourth additive, a fluorine-substituted boron ether compound, is introduced. The combined use of these four substances can form a more resilient composite protective film on the negative electrode, thereby enhancing the safety performance of the battery cell.

[0069] (2) The non-aqueous electrolyte of the present invention also contains an appropriate amount of ethyl propionate and lithium bis(trifluoromethanesulfonyl)imide which is more easily dissociated, thereby reducing the solvent viscosity, increasing the lithium ion transference number, greatly improving the wettability and ionic conductivity of the electrolyte, so as to improve the low-temperature disadvantage caused by the thicker SEI film with greater impedance due to the combined use of silane compounds and ring compounds, thereby improving the low-temperature performance of the battery cell.

[0070] (3) The present invention enables the lithium-ion battery prepared with silicon-doped negative electrode material to effectively improve the safety performance of the cell while taking into account the long cycle and low temperature performance of the cell through the synergistic effect of electrolyte and negative electrode material. Detailed Implementation

[0071] This invention discloses an electrolyte and a lithium-ion battery. Those skilled in the art can refer to the content of this document and appropriately modify the process parameters to achieve the desired results. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and applications of this invention have been described through preferred embodiments. Those skilled in the art can clearly modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit, and scope of this invention to implement and apply the technology of this invention.

[0072] All reagents and materials used in this invention are commercially available. The CAS numbers for Formulas T9 to T11 are as follows:

[0073] compound CAS number Type T9 CAS: 12523-60-3 Type T10 CAS: 381-59-9 Formula T11 CAS: 367-46-4

[0074] The present invention will be further illustrated below with reference to the embodiments:

[0075] Comparative Examples 1-7 and Examples 1-10

[0076] The lithium-ion batteries of Comparative Examples 1-7 and Examples 1-10 were all prepared according to the following preparation method, with the only difference being the choice of negative electrode and electrolyte, as shown in Table 1.

[0077] (1) Preparation of positive electrode

[0078] The positive electrode active material LiCoO2, the binder polyvinylidene fluoride (PVDF), and the conductive agent acetylene black were mixed in a weight ratio of 97.6:1.1:1.3. N-methylpyrrolidone (NMP) was added, and the mixture was stirred under vacuum until a uniform and fluid positive electrode slurry was formed. The positive electrode slurry was uniformly coated onto an aluminum foil with a thickness of 11 μm. The coated aluminum foil was baked in an oven with five different temperature gradients, and then dried in an oven at 120°C for 8 hours. Finally, it was rolled and slit to obtain the desired positive electrode sheet.

[0079] (2) Preparation of negative electrode sheet

[0080] Different negative electrode active materials (the specific composition and type of negative electrode active materials are shown in Table 1), conductive agent single-walled carbon nanotubes (SWCNT), conductive agent conductive carbon black (SP), binder sodium carboxymethyl cellulose (CMC) and binder styrene-butadiene rubber (SBR) were mixed in a weight ratio of 97.4:0.1:0.6:0.9:1.0 to form a slurry using a wet process. The slurry was coated onto the surface of a 6 μm thick copper foil for negative electrode current collectors. After drying (temperature: 85℃, time: 5h), rolling and die-cutting, the negative electrode sheet was obtained.

[0081] (3) Preparation of non-aqueous electrolyte

[0082] In an argon-filled glove box (moisture <10ppm, oxygen <1ppm), ethylene carbonate (EC), propylene carbonate (PC), and propyl propionate (PP) were mixed uniformly in a 1:1:1 mass ratio. LiPF6 (14wt% based on the total mass of the non-aqueous electrolyte), ethyl propionate (5-70wt% based on the total mass of the non-aqueous electrolyte, the specific amount of ethyl propionate is shown in Table 1), and additives (the specific amount and type of additives are shown in Table 1) were slowly added to the mixed solution and stirred until uniform to obtain the non-aqueous electrolyte.

[0083] (4) Preparation of the diaphragm

[0084] A 2μm thick composite layer of titanium dioxide and polyvinylidene fluoride-hexafluoropropylene copolymer was coated onto a 5μm thick polyethylene diaphragm.

[0085] (5) Preparation of lithium-ion batteries

[0086] The prepared positive electrode, separator, and negative electrode are wound together to obtain a bare cell without electrolyte injection. The bare cell is placed in an outer packaging foil, and the prepared electrolyte is injected into the dried bare cell. After vacuum sealing, settling, formation, shaping, and sorting, the desired lithium-ion battery is obtained.

[0087] Table 1. Lithium-ion batteries prepared in Comparative Examples 1-7 and Examples 1-10

[0088]

[0089] Note: " / " indicates that it has not been added.

[0090] Battery electrochemical performance testing

[0091] The electrochemical performance of the batteries obtained in Comparative Examples 1-7 and Examples 1-10 was tested, and the relevant descriptions are as follows:

[0092] ①25℃ cyclic experiment:

[0093] The battery obtained above was placed in an environment of (25±2)℃ and left to stand for 2-3 hours. When the battery body reached (25±2)℃, the battery was charged at a constant current of 1.5C with a cutoff current of 0.05C. After the battery was fully charged, it was left to stand for 5 minutes, and then discharged at a constant current of 0.7C until the cutoff voltage was 3.0V. The highest discharge capacity of the first 3 cycles was recorded as the initial capacity Q. When the number of cycles reached 800, the discharge capacity Q1 of the last cycle of the battery was recorded. The initial thickness T of the cell was recorded. The thickness after 300 cycles was recorded as T1. The recorded results are shown in Table 2.

[0094] Battery capacity retention rate (%) = Q1 / Q × 100%.

[0095] Thickness change rate (%) = (T1-T) / T × 100%

[0096] ② Low-temperature discharge experiment:

[0097] The battery obtained above was first discharged at 0.2C to 3.0V at an ambient temperature of (25±3)℃, and then left to rest for 5 minutes. It was then charged at 0.7C. When the cell terminal voltage reached the charging limit voltage, constant voltage charging was switched until the charging current was less than or equal to the cutoff current. Charging was then stopped, and the battery was left to rest for 5 minutes. It was then discharged at 0.2C to 3.0V, and the discharge capacity was recorded as the room temperature capacity Q2. The cell was then charged at 0.7C. When the cell terminal voltage reached the charging limit voltage, constant voltage charging was switched until the charging current was less than or equal to the cutoff current. The fully charged battery was left to rest at (-10±2)℃ for 4 hours, and then discharged at 0.4C to the cutoff voltage of 3.0V. The discharge capacity Q3 was recorded. The low-temperature discharge capacity retention rate was calculated, and the results are shown in Table 2.

[0098] Low-temperature discharge capacity retention rate of the battery (%) = Q3 / Q2 × 100%.

[0099] ③140℃ thermal shock test:

[0100] The battery obtained above was heated using convection or a circulating hot air chamber at an initial temperature of (25±3)℃, with a temperature change rate of (5±2)℃ / min. The temperature was increased to (140±2)℃ and held for 60 minutes before the test was ended. The battery status was recorded, and the results are shown in Table 2.

[0101] ④ Overcharge test:

[0102] The battery obtained above was charged to 5V at a constant current rate of 3C, and the battery status was recorded. The results are shown in Table 2.

[0103] ⑤ Acupuncture test:

[0104] The battery obtained above is pierced with a high-temperature resistant steel needle with a diameter of ф5-8mm (the needle tip has a conical angle of 45℃-60℃, and the needle surface is smooth and free of rust, oxide layer, and oil stains) at a speed of (25±5)mm / s, perpendicular to the battery plates. The piercing point should be close to the geometric center of the pierced surface (the steel needle should remain inside the battery). The test is stopped when the battery surface temperature drops to the peak temperature of 10℃ or below after 1 hour.

[0105] Table 2 shows the battery test results obtained from Comparative Examples 1-7 and Examples 1-10.

[0106]

[0107]

[0108] As can be seen from the results in Table 2, by comparing Comparative Examples 1, 2, 6 and Example 1, it is clear that the effect of using tetravinylsilane (first additive) or bicyclic compound (second additive) alone is not good.

[0109] By comparing Comparative Examples 1, 2 and 3, Comparative Example 3 showed that the simultaneous addition of tetravinylsilane and bicyclic compounds significantly improved the cycle performance and safety performance.

[0110] By comparing Comparative Examples 3, 4 and 5, Comparative Example 4 further added a third additive, lithium difluorooxalate borate, to Comparative Example 3, and Comparative Example 5 further added lithium salt bis(trifluoromethanesulfonyl)imide to Comparative Example 4. The cycle performance and safety performance of Comparative Example 5 were further improved.

[0111] Furthermore, as can be seen from Comparative Example 7 and Example 1, A / B is ineffective when it exceeds the scope defined by the present invention.

[0112] By comparing Example 1 and Example 7, Example 7, based on Example 1, further added a fourth additive, a fluorinated substituted boron ether compound, and the cycle performance of Example 7 was significantly improved.

[0113] By comparing Examples 1-6, and by replacing different types and contents of additives, different lithium salt contents, and different ethyl propionate contents, Examples 1-6 all showed good results in terms of cycle performance and safety performance.

[0114] By comparing Examples 7-10, with different types and contents of additives, different lithium salt contents, different ethyl propionate contents, and different types and contents of fluorinated boron ether compounds, Examples 7-10 showed excellent cycling performance and safety performance.

[0115] In summary, by adding ethyl propionate, lithium difluorooxalate boronate, silane compounds, bicyclic compounds, lithium bis(trifluoromethanesulfonyl)imide, and fluorine-substituted boron ether compounds to the electrolyte in a complete combination, and with the A / B ratio within a suitable range, the synergistic effect between the additives and solvents, particularly the combined use of tetravinylsilane and bicyclic compounds, allows for the cross-linking of these two substances at a specific ratio to form a thicker and more stable SEI protective film on the negative electrode surface. This prevents the electrolyte from being reduced on the negative electrode surface, mitigating the problem of increased cycle expansion caused by silicon-doped negative electrodes, thereby improving battery safety and cycle life. Furthermore, the introduction of fluorine-substituted boron ether compounds and lithium difluorooxalate boronate, combined with these four substances, forms a more resilient composite protective film on the negative electrode, further enhancing the safety performance of the battery cell.

[0116] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An electrolyte, characterized in that, The electrolyte comprises an organic solvent, a lithium salt, a first additive, a second additive, and a third additive; The first additive includes silane compounds; The second additive includes bicyclic compounds; The third additive includes lithium difluorooxalate borate; The silane compounds include tetravinylsilane; The cyclic compounds include at least one of the compounds shown in Formulas T1 to T8; ； The amount of the first additive is 0.2 wt% to 1 wt% of the total mass of the electrolyte. The amount of the second additive is 1 wt% to 5 wt% of the total mass of the electrolyte; The amount of the third additive is 0.1 wt% to 1 wt% of the total mass of the electrolyte. The amounts of the first additive and the second additive shall satisfy the following conditions: 0.07≤C A / C B ≤0.8; Among them, C A C indicates the amount of the first additive added. B This indicates the amount of the second additive added.

2. The electrolyte according to claim 1, characterized in that, The organic solvent includes a first organic solvent, or includes both a first organic solvent and a second organic solvent; The first organic solvent includes ethyl propionate; The second organic solvent includes at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, propyl propionate, and propyl acetate.

3. The electrolyte according to claim 2, characterized in that, The amount of the first organic solvent added accounts for 5 wt% to 70 wt% of the total mass of the electrolyte.

4. The electrolyte according to claim 1, characterized in that, The lithium salt includes lithium hexafluorophosphate and / or lithium bis(trifluoromethanesulfonyl)imide.

5. The electrolyte according to claim 4, characterized in that, The amount of lithium hexafluorophosphate added is 13wt% to 20wt% of the total mass of the electrolyte; and / or, The amount of lithium bis(trifluoromethanesulfonyl)imide added is 0.5 wt% to 10 wt% of the total mass of the electrolyte.

6. The electrolyte according to any one of claims 1-5, characterized in that, The electrolyte also includes a fourth additive and / or a fifth additive; The fourth additive includes at least one of tris(trimethylsilane) phosphite, tris(trimethylsilyl) borate, lithium difluorosulfonylimide, 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, vinyl sulfite, vinyl sulfate, vinylene carbonate, fluorovinyl carbonate, lithium dioxaborate, lithium difluorooxaborate phosphate, and vinyl ethylene carbonate. The fifth additive includes fluorinated boron ether compounds.

7. The electrolyte according to claim 6, characterized in that, The amount of the fourth additive is 0-10 wt% of the total mass of the electrolyte.

8. The electrolyte according to claim 6, characterized in that, The fluorine-substituted boron ether compounds include at least one of the compounds shown in Formulas T9 to T11; 。 9. The electrolyte according to claim 6, characterized in that, The amount of the fluorine-substituted boron ether compound added is 0.1 wt% to 1 wt% of the total mass of the electrolyte.

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte as described in any one of claims 1-9; The negative electrode active material of the negative electrode sheet contains silicon-based materials.

11. The lithium-ion battery according to claim 10, characterized in that, The silicon-based material is selected from at least one of silicon, silicon-carbon, SiOx, and SiO2, wherein 0 <x<2。 12. The lithium-ion battery according to claim 10 or 11, characterized in that, The negative electrode active material of the negative electrode sheet also includes carbon materials.

13. The lithium-ion battery according to claim 12, characterized in that, Carbon materials include at least one of artificial graphite, natural graphite, mesophase carbon microspheres, hard carbon, and soft carbon.

14. The lithium-ion battery according to claim 12, characterized in that, The mass ratio of the silicon-based material to the carbon material is (1~40):(60~99).

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