An electrolyte additive, an electrolyte, and a lithium-ion battery

Abstract

This invention belongs to the field of lithium-ion battery technology, and provides an electrolyte additive, an electrolyte, and a lithium-ion battery. The electrolyte additive includes a functional additive, the structural formula of which is shown below. The functional additive of this invention forms a stable CEI film through the synergistic effect of borate ester groups, phenyl groups, and cyano groups, effectively preventing the dissolution of transition metal ions in the positive electrode material, improving the high-temperature performance of the lithium-ion battery, and solving the problem of rapid performance degradation of lithium-ion batteries under high-temperature environments in the prior art.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to an electrolyte additive, an electrolyte, and a lithium-ion battery. Background Technology

[0002] With the surge in demand for high-energy-density batteries from new energy vehicles, energy storage systems, and consumer electronics, lithium-ion batteries have become the mainstream choice due to their superior energy density. However, the rapid performance degradation of lithium-ion batteries at high temperatures (>45℃) has become a core pain point and industry bottleneck restricting their widespread application. For lithium-ion batteries, high temperatures not only accelerate electrolyte decomposition, trigger phase transitions in the cathode material structure and dissolution of transition metal ions, leading to irreversible capacity loss and a sharp drop in cycle life, but also exacerbate interfacial side reactions, significantly increasing the risk of thermal runaway and posing a safety threat. Especially in harsh operating conditions such as high-temperature regions, fast-charging / high-rate applications, and closed battery packs, the internal temperature rise problem of lithium-ion batteries is more prominent, making high-temperature stability a key performance indicator determining the reliability, safety, and market acceptance of lithium-ion batteries.

[0003] Chinese patent CN113690487B discloses a secondary battery electrolyte and a secondary battery. Although it improves the high-temperature stability of the battery by introducing an additive containing BO, the capacity retention rate of the battery after 300 cycles at 45°C is still less than 75%, which needs to be further improved.

[0004] Therefore, there is still a need to develop lithium-ion batteries with better high-temperature performance. Summary of the Invention

[0005] To address the problem of rapid performance degradation of lithium-ion batteries under high-temperature environments in existing technologies, this invention provides an electrolyte additive, an electrolyte, and a lithium-ion battery.

[0006] This invention is achieved through the following technical solution:

[0007] In a first aspect, the present invention provides an electrolyte additive, including a functional additive, the functional additive having the structural formula shown in Formula I:

[0008]

[0009] R1, R2, R3, R4 and R5 are each independently selected from H, halogen, alkyl, cyano, unsubstituted phenyl and cyano-substituted phenyl, and at least one of R1, R2, R3, R4 and R5 contains a cyano group.

[0010] Preferably, the functional additive is one of the following compounds:

[0011] .

[0012] Preferably, the electrolyte additive further includes sulfur-based additives, carbonate additives, silane additives and lithium salt additives, and the mass ratio of the functional additives, sulfur-based additives, carbonate additives, silane additives and lithium salt additives is (0.3~0.5):(0.5~1.5):(0.2~0.5):(0.2~0.5):(0.5~1).

[0013] Furthermore, the sulfur-based additive is vinyl sulfate, 1,3-propanesulfonate lactone, or methanedisulfonate methylene ester.

[0014] Furthermore, the carbonate additive is ethylene carbonate.

[0015] Furthermore, the silane additive is tetraethylenesilane or vinyltrimethylsilane.

[0016] Furthermore, the lithium salt additive is lithium difluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(oxalate-borate) or lithium bis(fluorooxalate-borate).

[0017] In a second aspect, the present invention provides an electrolyte comprising an organic solvent, a lithium salt, and electrolyte additives as described above.

[0018] Preferably, the lithium salt in the electrolyte is lithium hexafluorophosphate.

[0019] Thirdly, the present invention provides a lithium-ion battery comprising the electrolyte as described above.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The functional additive provided by this invention contains three functional groups: phenyl, cyano, and borate ester. These three functional groups work synergistically to significantly improve the high-temperature performance of lithium-ion batteries. First, the boron-containing compound generated from the decomposition of the borate ester crosslinks with the oxidation product of the phenyl group (polyaromatic hydrocarbon) to form an "organic-inorganic hybrid cathode electrolyte interphase (CEI) film." The phenyl group provides the framework, while the boron-containing compound fills the voids, enhancing the density of the CEI film and effectively preventing the dissolution of transition metal ions from the cathode material, thus improving the high-temperature performance of the lithium-ion battery. Simultaneously, the rigid structure of the phenyl group and the boron-containing compound synergistically enhance the thermal stability of the CEI film, suppressing exothermic interfacial reactions at high temperatures. Second, the cyano group complexes with dissolved transition metal ions at the cathode, reducing the probability of transition metal ions catalyzing electrolyte decomposition. Furthermore, the cyano group complexes with the transition metal ions, and the boron ester ester provides the boron-containing compound; the two interact to form a "BOM" (where M is the transition metal) inert layer, anchoring the transition metal ions and further reducing their dissolution. Therefore, the functional additive of the present invention forms a stable CEI film through the synergistic effect of borate ester group, phenyl group and cyano group, which effectively prevents the dissolution of transition metal ions and improves high temperature performance.

[0022] Furthermore, this invention introduces sulfide additives, carbonate additives, silane additives, and lithium salt additives into the electrolyte additives. Sulfide additives can form a dense and stable solid electrolyte interphase (SEI) film on the negative electrode surface, thereby inhibiting the continuous decomposition of the electrolyte, reducing battery impedance, and improving lithium-ion migration efficiency. Carbonate additives, after being added to the electrolyte, preferentially reduce on the negative electrode during formation, participating in the formation of the SEI film. Silane additives have the ability to coordinate with lithium ions, participating in the solvation shell of lithium ions, and undergoing reduction and decomposition on the electrode surface as lithium ions migrate, thereby obtaining an SEI film rich in inorganic lithium salts. This regulates the electrode interface composition, improves lithium-ion transport performance, and enhances the rate performance of lithium-ion batteries. Silane additives can also reduce the gas generation behavior of high-nickel materials at high temperatures. Lithium salt additives decompose into films at both the positive and negative electrodes, resulting in dense films and reduced impedance. Therefore, the introduction of sulfur-based additives, carbonate additives, silane additives, and lithium salt additives further improves the high-temperature performance of lithium-ion batteries. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 The results of high-temperature cycle performance tests of lithium-ion batteries corresponding to the embodiments and comparative examples of this invention are shown.

[0025] Figure 2 The high-temperature storage performance test results of the lithium-ion batteries corresponding to the embodiments and comparative examples of the present invention are shown.

[0026] Figure 3 This is the electrochemical window of the lithium-ion battery corresponding to Example 1 of the present invention. Detailed Implementation

[0027] 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.

[0028] It should be noted that the process equipment or apparatus not specifically mentioned in the following embodiments are all conventional equipment or apparatus in the art.

[0029] It should be noted that the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products, or apparatuses. Furthermore, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not intended to limit the order of the method steps or define the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0030] The electrolyte additive provided by this invention includes a functional additive, the structural formula of which is shown in Formula I:

[0031]

[0032] R1, R2, R3, R4 and R5 are each independently selected from H, halogen, alkyl, cyano, unsubstituted phenyl and cyano-substituted phenyl, and at least one of R1, R2, R3, R4 and R5 contains a cyano group.

[0033] Specifically, the functional additive is one of the following compounds:

[0034] .

[0035] The functional additive of this invention contains phenyl, cyano, and borate ester groups. The boron-containing compound generated from the decomposition of the borate ester group crosslinks with the oxidation product of the phenyl group (polyaromatic hydrocarbon) to form an "organic-inorganic hybrid CEI film." The phenyl group provides the framework, while the boron-containing compound fills the gaps, enhancing the density of the CEI film and effectively preventing the dissolution of transition metal ions from the cathode material, thus improving the high-temperature performance of lithium-ion batteries. Simultaneously, the rigid structure of the phenyl group and the boron-containing compound synergistically enhance the thermal stability of the CEI film, suppressing exothermic interfacial reactions at high temperatures. The cyano group complexes with dissolved transition metal ions at the cathode, reducing the catalytic decomposition of the electrolyte by transition metal ions; the cyano group complexes with transition metal ions, and the borate ester group provides the boron-containing compound, forming a "BOM" (where M is the transition metal) inert layer that anchors the transition metal ions, further reducing their dissolution. Therefore, the synergistic effect of the borate ester group, phenyl group, and cyano group in the functional additive of this invention forms a stable CEI film, effectively preventing the dissolution of transition metal ions and improving the high-temperature performance of lithium-ion batteries.

[0036] In some preferred embodiments of the present invention, the electrolyte additive may further include sulfide additives, carbonate additives, silane additives and lithium salt additives; wherein the mass ratio of the functional additives, sulfide additives, carbonate additives, silane additives and lithium salt additives is (0.3~0.5):(0.5~1.5):(0.2~0.5):(0.2~0.5):(0.5~1).

[0037] In some embodiments of the present invention, the sulfur-based additive is ethylene sulfate (DTD), 1,3-propane sulfonate (PS), or methylene methane disulfonate (MMDS).

[0038] The sulfur-based additives can form a dense and stable SEI film on the negative electrode surface, thereby inhibiting the continuous decomposition of the electrolyte, reducing the impedance of the lithium-ion battery, and improving the migration efficiency of lithium ions. The sulfur-based additives can also form a CEI film on the positive electrode surface, preventing corrosion of the positive electrode material and excessive decomposition of the electrolyte.

[0039] In some embodiments of the present invention, the carbonate additive is ethylene carbonate (VC). VC is an unsaturated compound that readily gains electrons and is reduced at the negative electrode. After being added to the electrolyte, the carbonate additive preferentially reduces at the negative electrode compared to other solvents during formation, participating in the formation of the SEI film. The SEI film formed by VC at the negative electrode is a pectin-like polymer with high content, exhibiting good hydrophilicity, which is beneficial for electrolyte retention on the negative electrode SEI film and reduces the negative impact of localized electrolyte drying.

[0040] In some embodiments of the present invention, the silane additive is tetraethylenesilane (TVSi) or vinyltrimethylsilane.

[0041] The silane additives possess the ability to coordinate with lithium ions, participating in the solvation shell of lithium ions. As lithium ions migrate, they undergo reduction and decomposition on the electrode surface, thereby obtaining an SEI film rich in inorganic lithium salts. This regulates the electrode interface composition, improves lithium ion transport performance, and enhances the rate performance of lithium-ion batteries. Silane additives can also reduce gas generation behavior in high-nickel materials at high temperatures.

[0042] In some embodiments of the present invention, the lithium salt additive is lithium difluorophosphate (LiPO2F2), lithium bis(fluorosulfonyl)imide, lithium bis(oxalate borate) (LiBOB), or lithium bis(oxalate borate) (LiODFB).

[0043] The lithium salt additive mainly functions to decompose into films at the positive and negative electrodes, resulting in dense films and reducing the impedance of lithium-ion batteries.

[0044] Based on the electrolyte additives described above, the electrolyte provided by the present invention includes an organic solvent, a lithium salt, and electrolyte additives.

[0045] The organic solvent includes cyclic carbonates and chain carbonates, wherein the cyclic carbonates include fluoroethylene carbonate and ethylene carbonate, and the chain carbonates include dimethyl carbonate and ethyl methyl carbonate.

[0046] In some embodiments of the present invention, the ratio of the total volume of fluoroethylene carbonate and ethylene carbonate, the volume of dimethyl carbonate and the volume of methyl ethyl carbonate is (20~24):(50~65):(13~20).

[0047] In some embodiments of the present invention, the lithium salt is lithium hexafluorophosphate (LiPF6), the mass percentage of the lithium salt in the electrolyte is 11% to 16%, and the mass percentage of the electrolyte additive is 0.3% to 4%.

[0048] Example 1

[0049] Based on the mass percentage of the components, the electrolyte formulation used in this embodiment is as follows: 0.3% functional additive (compound of formula I-1, 3-methyl-4-cyanoboronate pinacol ester), 14% LiPF6, and the balance being organic solvent. The organic solvent in the above electrolyte formulation consists of fluoroethylene carbonate, ethylene carbonate, dimethyl carbonate, and methyl ethyl carbonate. Based on the total volume of the organic solvent being 100%, the volume percentage of fluoroethylene carbonate is 2%, ethylene carbonate is 20%, dimethyl carbonate is 60%, and methyl ethyl carbonate is 18%.

[0050]

[0051] Example 2

[0052] Based on the mass percentage of the components, the electrolyte formulation used in this embodiment is as follows: 0.5% functional additive (compound of formula I-1, 3-methyl-4-cyanoboronate pinacol ester), 14% LiPF6, and the balance being organic solvent. The organic solvent in the above electrolyte formulation consists of fluoroethylene carbonate, ethylene carbonate, dimethyl carbonate, and methyl ethyl carbonate. Based on the total volume of the organic solvent being 100%, the volume percentage of fluoroethylene carbonate is 2%, ethylene carbonate is 20%, dimethyl carbonate is 60%, and methyl ethyl carbonate is 18%.

[0053] Example 3

[0054] Based on the mass percentage of the components, the electrolyte formulation used in this embodiment is as follows: 0.5% functional additive (compound of formula I-1), 0.5% LiBOB, 0.5% PS, 0.3% VC, 14% LiPF6, 0.2% TVSi, and the balance being organic solvent. The organic solvent in the above electrolyte formulation consists of fluoroethylene carbonate, ethylene carbonate, dimethyl carbonate, and methyl ethyl carbonate. Based on the total volume of the organic solvent being 100%, the volume percentage of fluoroethylene carbonate is 2%, ethylene carbonate is 20%, dimethyl carbonate is 60%, and methyl ethyl carbonate is 18%.

[0055] Example 4

[0056] This embodiment provides an electrolyte that differs from Example 3 only in that the functional additive in the electrolyte is compound I-2 (4-cyanobiphenyl-4-boronic acid pinacol ester), while the other conditions are the same as in Example 3.

[0057]

[0058] Example 5

[0059] This embodiment provides an electrolyte that differs from Example 3 only in that the functional additive in the electrolyte is compound I-3 (2-cyano-3-fluorophenylboronic acid pinacol ester), and the other conditions are the same as in Example 3.

[0060]

[0061] Example 6

[0062] This embodiment provides an electrolyte that differs from Example 3 only in that the amount of sulfur-containing additive PS is adjusted to 1%, while other conditions are the same as in Example 3.

[0063] Example 7

[0064] This embodiment provides an electrolyte that differs from Example 3 only in that the sulfur-containing additive PS is replaced with DTD, and the addition amount is 1.5%, while other conditions are the same as in Example 3.

[0065] Example 8

[0066] This embodiment provides an electrolyte that differs from Example 3 only in that the sulfur-containing additive PS is replaced with MMDS, while other conditions are the same as in Example 3.

[0067] Example 9

[0068] This embodiment provides an electrolyte that differs from Example 3 only in that the amount of VC added in Example 3 is adjusted to 0.5%, while other conditions are the same as in Example 3.

[0069] Example 10

[0070] This embodiment provides an electrolyte that differs from Example 3 only in that TVSi in Example 3 is replaced with allyltrimethylsilane, and the amount added is 0.5%, while other conditions are the same as in Example 3.

[0071] Example 11

[0072] This embodiment provides an electrolyte that differs from Example 3 only in that the amount of LiPF6 added in Example 3 is adjusted to 12%, while other conditions are the same as in Example 3.

[0073] Example 12

[0074] This embodiment provides an electrolyte that differs from Example 3 only in that the amount of LiPF6 added in Example 3 is adjusted to 15%, while other conditions are the same as in Example 3.

[0075] Example 13

[0076] This embodiment provides an electrolyte that differs from that of Example 3 only in that LiBOB in Example 3 is replaced with LiPO2F2, while other conditions are the same as in Example 3.

[0077] Example 14

[0078] This embodiment provides an electrolyte that differs from Embodiment 3 only in that LiBOB in Embodiment 3 is replaced with LiODFB, while other conditions are the same as in Embodiment 3.

[0079] Comparative Example 1

[0080] This comparative example provides an electrolyte that differs from Example 1 only in that the electrolyte does not contain the functional additive of Formula I-1, but contains the additive of Formula I-4. The difference between the functional additive in Example 1 and the additive of Formula I-4 is that the additive of Formula I-4 does not contain cyano groups.

[0081]

[0082] Comparative Example 2

[0083] This comparative example provides an electrolyte that differs from Example 1 only in that the electrolyte does not contain the functional additive of Formula I-1, but contains the additive of Formula I-5. The difference between the functional additive in Example 1 and the additive of Formula I-5 is that the additive of Formula I-5 does not contain borate ester groups.

[0084]

[0085] Comparative Example 3

[0086] This comparative example provides an electrolyte that differs from Example 3 only in that the electrolyte does not contain functional additives, while other conditions are the same as in Example 3.

[0087] Lithium-ion battery assembly: Graphite is used as the negative electrode active material. A negative electrode slurry is prepared by mixing graphite, conductive agent acetylene black, binder carboxylmethyl cellulose (CMC), and styrene-butadiene rubber (SBR) in a mass ratio of 95.4:1.5:1.4:1.7. The negative electrode slurry is coated onto a copper foil current collector and vacuum dried to obtain the negative electrode sheet. NCM811 is used as the positive electrode active material. A positive electrode slurry is prepared by mixing the positive electrode active material, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) in a mass ratio of 96.5:2.2:1.3. The positive electrode slurry is coated onto an aluminum foil current collector and vacuum dried to obtain the positive electrode sheet. The electrolytes prepared in the examples and comparative examples are used to assemble the above-mentioned positive electrode sheet, negative electrode sheet, and separator into lithium-ion batteries.

[0088] NCM811 is a typical type of cathode material for ternary lithium-ion batteries, belonging to lithium nickel cobalt manganese oxide (LiNi). x Co y Mn z O) system.

[0089] The electrical performance of the assembled lithium-ion battery is then tested:

[0090] (1) High-temperature cycling performance test

[0091] At 45℃, the lithium-ion battery was charged at a constant current of 1C (nominal capacity) to a voltage of 4.25V, then charged at a constant voltage of 4.25V until the current ≤0.05C. After resting for 10 minutes, it was discharged at a constant current of 1C to a cutoff voltage of 2.8V. This constitutes one charge-discharge cycle. The lithium-ion battery was subjected to 350 charge-discharge cycles at 45℃ under the above conditions. The capacity retention rate was calculated using the following formula, and the results are shown below. Figure 1 .

[0092] Capacity retention rate (%) of a lithium-ion battery after N cycles = (Discharge capacity in the Nth cycle / Initial discharge capacity) × 100%

[0093] Where N is the number of charge-discharge cycles.

[0094] (2) High-temperature storage performance test of lithium-ion batteries

[0095] The lithium-ion battery was charged at a constant current of 1C (nominal capacity) to a voltage of 4.25V, then charged at a constant voltage of 4.25V until the current ≤0.05C. After resting for 10 minutes, it was discharged at a constant current of 1C to 2.8V. This constituted one charge-discharge cycle. The lithium-ion battery was subjected to three charge-discharge cycles at 25℃ with a charge-discharge rate of 1C, and then fully charged at a 1C rate. The capacity Q0 of the lithium-ion battery was recorded. The fully charged lithium-ion battery was stored at 50℃ for 50 days, and the 1C discharge capacity Q1 of the lithium-ion battery was recorded. Then, the lithium-ion battery was charged and discharged at 25℃ with a 1C rate for 2 weeks, and the 1C discharge capacity Q2 was recorded. The experimental data of high-temperature storage capacity retention rate and capacity recovery rate of the lithium-ion battery were calculated. See [link to relevant documentation]. Figure 2 The calculation formulas used are as follows:

[0096] Capacity retention rate (%) = Q1 / Q0 × 100%

[0097] Capacity recovery rate (%) = Q2 / Q0 × 100%

[0098] Combination Figure 1 and Figure 2 Comparing Example 1 and Comparative Examples 1-2, it can be seen that the electrolyte of Example 1, by introducing the functional additive shown in Formula I-1, can significantly improve the high-temperature storage performance and high-temperature cycle performance of the lithium-ion battery. This is mainly because the functional additive introduced in this invention contains borate ester groups, phenyl groups, and cyano groups. The three functional groups work synergistically to significantly improve the high-temperature performance of the lithium-ion battery. Although the additive in Comparative Example 1 also contains borate ester groups and phenyl groups, it does not contain cyano groups. Therefore, the quality of the positive electrode film is poor, resulting in poor high-temperature performance of its corresponding lithium-ion battery. The additive in Comparative Example 2 does not contain borate ester groups, and the film quality is not as good as that of the functional additive in Example 1. Therefore, the high-temperature performance of its corresponding lithium-ion battery is also not as good as that of the lithium-ion battery corresponding to Example 1. The electrolyte of Comparative Example 3 does not contain any additives. Therefore, the high-temperature storage performance and high-temperature cycle performance of its lithium-ion battery are weaker than those of the lithium-ion batteries corresponding to Comparative Examples 1 and 2.

[0099] from Figure 1It can be seen that, compared with Example 1, the increased amount of functional additives in Example 2 improved the high-temperature cycle performance of the resulting lithium-ion battery, further proving the improving effect of the functional additives of the present invention on the high-temperature cycle performance of lithium-ion batteries. Compared with Example 2, the addition of other additives in Example 3 further improved the high-temperature cycle performance of the lithium-ion battery. Furthermore, compared with Example 3, the use of compound I-2 as a functional additive in Example 4 further improved the high-temperature cycle performance of the lithium-ion battery. This is because the number of phenyl groups in compound I-2 is greater than that in compound I-1, further illustrating the role of phenyl groups in improving the high-temperature cycle performance of lithium-ion batteries. Compared with Example 3, the use of sulfur-based additives DTD and MMDS in Examples 7 and 8, respectively, resulted in superior high-temperature cycle performance of the lithium-ion battery. The performance data from Example 10 shows that allyltrimethylsilane significantly improves the high-temperature cycle performance of lithium-ion batteries compared to TVSi. Comparing Examples 3, 11, and 12, it can be seen that the lithium-ion battery exhibits the best high-temperature cycle performance when the lithium salt mass fraction is 12%.

[0100] from Figure 3 It can be seen that the electrolyte composed of 0.3% functional additive, lithium salt, and organic solvent in Example 1 has an electrochemical window of 4.7V, indicating that the electrolyte has a strong ability to resist oxidation and reduction reactions, and will not easily decompose or undergo other irreversible electrochemical reactions within a wide voltage range, thus maintaining its own chemical stability.

[0101] In summary, the functional additives of the present invention with the structure shown in Formula I do not act independently of a single functional group, but rather the entire structure produces a multifaceted synergistic effect in the electrolyte. This synergistic effect is the key to improving the performance and stability of lithium-ion batteries.

[0102] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. An electrolyte additive characterized in that, The functional additive has a structural formula of: 。 2. The electrolyte additive according to claim 1, characterized in that, The electrolyte additive further comprises a sulfur additive, a carbonate additive, a silane additive and a lithium salt additive, and the mass ratio of the functional additive, the sulfur additive, the carbonate additive, the silane additive and the lithium salt additive is (0.3-0.5):(0.5-1.5):(0.2-0.5):(0.2-0.5):(0.5-1).

3. The electrolyte additive according to claim 2, characterized in that, The sulfur additive is vinyl sulfate, 1,3-propane sulfonic acid lactone or methane disulfonic acid methylene ester.

4. The electrolyte additive according to claim 2, characterized in that, The carbonate additive is vinyl carbonate.

5. The electrolyte additive according to claim 2, characterized in that, The silane additive is tetraethylenyl silane or vinyl trimethyl silane.

6. The electrolyte additive according to claim 2, characterized in that, The lithium salt additive is lithium difluorophosphate, lithium bisfluorosulfonylimide, lithium bisoxalate borate or lithium bisfluoroxalate borate.

7. An electrolyte, characterized by The electrolyte additive comprises an organic solvent, a lithium salt and the electrolyte additive of any one of claims 1-6.

8. The electrolyte of claim 7, wherein, The lithium salt is lithium hexafluorophosphate.

9. A lithium-ion battery, characterized by The electrolyte comprises the electrolyte of claim 7.

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