Electrolyte additive, electrolyte and lithium ion battery

Abstract

The invention belongs to the technical field of lithium ion batteries, and provides an electrolyte additive, an electrolyte and a lithium ion battery, the electrolyte additive comprises a functional additive, and the structural formula of the functional additive is shown in the specification. According to the functional additive disclosed by the invention, a stable CEI film is formed through the synergistic effect of boric acid ester group, phenyl and cyano group, so that the dissolution of transition metal ions in the positive electrode material is effectively prevented, the high-temperature performance of the lithium ion battery is improved, and the problem that the performance of the lithium ion battery in a high-temperature environment is quickly attenuated and degraded in the prior art is solved.

Description

Technical Field

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

[0002] With the surge in demand for high-energy-density batteries in 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 in high-temperature environments (>45°C) has become a core pain point and industry bottleneck restricting their widespread application. For lithium-ion batteries, high temperatures not only accelerate the decomposition of the electrolyte, trigger structural phase changes in the positive electrode material and the 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 high-temperature areas, fast-charging / high-rate applications, and closed battery packs, the problem of internal temperature rise in lithium-ion batteries is more prominent. High-temperature stability has become a key performance indicator that determines the reliability, safety, and market acceptance of lithium-ion batteries.

[0003] Chinese patent CN113690487B discloses a secondary battery electrolyte and a secondary battery. Although the high-temperature stability of the battery is improved by introducing a BO-containing additive, 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] In order to solve the problem of rapid performance degradation of lithium-ion batteries in high-temperature environments in the prior art, the present invention provides an electrolyte additive, an electrolyte and a lithium-ion battery.

[0006] The present invention is achieved through the following technical solutions: In a first aspect, the present invention provides an electrolyte additive, including a functional additive, wherein the structural formula of the functional additive is shown in Formula I:

[0007] wherein R1, R2, R3, R4 and R5 are 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 cyano.

[0008] Preferably, the functional additive is one of the following compounds: .

[0009] Preferably, 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).

[0010] Further, the sulfur additive is vinyl sulfate, 1,3-propane sultone or methylene methane disulfonate.

[0011] Further, the carbonate additive is vinyl carbonate.

[0012] Further, the silane additive is tetraethylenesilane or vinyltrimethylsilane.

[0013] Further, the lithium salt additive is lithium difluorophosphate, lithium bisfluorosulfonylimide, lithium bisoxalate borate or lithium bisfluoroxalate borate.

[0014] In a second aspect, the present application provides an electrolyte comprising an organic solvent, a lithium salt and the electrolyte additive as described above.

[0015] Preferably, the lithium salt in the electrolyte is lithium hexafluorophosphate.

[0016] In a third aspect, the present application provides a lithium ion battery comprising the electrolyte as described above.

[0017] Compared with the prior art, the present application has the following advantages: The functional additive provided by the present application contains three functional groups of phenyl, cyano and borate, which can significantly improve the high-temperature performance of lithium ion batteries through synergistic effect. First, the borate decomposes to generate a boron-containing compound which crosslinks with the oxidation product (polyaromatic hydrocarbon) of the phenyl to form an "organic-inorganic hybrid cathode electrolyte interphase (CEI) film", in which the phenyl provides a skeleton and the boron-containing compound fills the voids to enhance the compactness of the CEI film, effectively preventing the dissolution of transition metal ions in the positive electrode material and improving the high-temperature performance of lithium ion batteries. At the same time, the rigid structure of the phenyl synergistically enhances the thermal stability of the CEI film with the boron-containing compound, and inhibits the interface exothermic reaction at high temperature. Second, the cyano complex with the dissolved transition metal ions in the positive electrode reduces the probability of electrolyte decomposition catalyzed by transition metal ions; and the cyano complex with transition metal ions and the borate provides boron-containing compounds, which interact with each other to form a "B-O-M" (M is a transition metal) inert layer to anchor the transition metal ions and further reduce the dissolution of transition metal ions. Therefore, the functional additive of the present application forms a stable CEI film through the synergistic effect of borate, phenyl and cyano, effectively prevents the dissolution of transition metal ions and improves the high-temperature performance.

[0018] Further, the present application introduces sulfur-based additives, carbonate-based additives, silane-based additives and lithium salt additives into the electrolyte additives. The sulfur-based 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 the impedance of the battery and improving the migration efficiency of lithium ions. After the carbonate-based additive is added to the electrolyte, it is preferentially reduced on the negative electrode during formation and participates in the formation of the SEI film. The silane additive has the ability to coordinate with lithium ions and can participate in the solvation shell of lithium ions and be reduced and decomposed on the electrode surface as the lithium ions migrate, thereby obtaining an SEI film rich in inorganic lithium salt, regulating the composition of the electrode interface and improving the transmission performance of lithium ions and the rate performance of lithium ion batteries. The silane-based additive can also reduce the gas generation behavior of high-nickel materials at high temperature. The lithium salt additive decomposes into a film on the positive and negative electrodes, and the film has good compactness and low impedance. Therefore, the introduction of sulfur-based additives, carbonate-based additives, silane-based additives and lithium salt additives further improves the high-temperature performance of lithium ion batteries. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort, based on these drawings.

[0020] Figure 1 The high-temperature cycle performance test results of the lithium ion batteries corresponding to the examples and comparative examples of the present application; Figure 2 The high-temperature storage performance test results of the lithium ion batteries corresponding to the examples and comparative examples of the present application; Figure 3 The electrochemical window of the lithium ion battery corresponding to Example 1 of the present application. DETAILED DESCRIPTION

[0021] The embodiments of the present application will be described in detail below with specific examples. Those skilled in the art can easily understand other advantages and effects of the present application from the content disclosed in the specification. The present application can also be implemented or applied by different specific embodiments, and various modifications or changes can be made to the details in the specification without departing from the spirit of the present application.

[0022] It should be noted that the process equipment or device not specifically mentioned in the following examples is the conventional equipment or device in the art.

[0023] 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 device comprising a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices. Moreover, unless otherwise specified, the numbering of each method step is only a convenient tool to identify each method step, and is not a limitation on the arrangement order of each method step or a limitation on the scope of the present application. Changes or adjustments of the relative relationship, without substantial changes in the technical content, are also considered as the scope of the present application.

[0024] The electrolyte additive provided by the present application comprises a functional additive, and the structural formula of the functional additive is shown as formula I:

[0025] wherein 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 group of R1, R2, R3, R4 and R5 comprises cyano.

[0026] Specifically, the functional additive is one of the following compounds: .

[0027] The functional additive contains phenyl, cyano and borate groups. The borate groups decompose to form a boron-containing compound which crosslinks with the oxidation product of phenyl (polyaromatic hydrocarbon) to form an "organic-inorganic hybrid CEI film". The phenyl provides a skeleton, and the boron-containing compound fills the voids to enhance the compactness of the CEI film, effectively preventing the dissolution of transition metal ions in the positive electrode material and improving the high-temperature performance of the lithium ion battery. At the same time, the rigid structure of the phenyl and the boron-containing compound synergistically enhance the thermal stability of the CEI film, inhibiting the interface exothermic reaction at high temperatures. The cyano group complexes with the dissolved transition metal ions in the positive electrode, reducing the catalytic decomposition of the electrolyte by transition metal ions; the cyano group complexes with transition metal ions, and the borate group provides a boron-containing compound, both of which form an "B-O-M" (M is a transition metal) inert layer to anchor the transition metal ions, further reducing the dissolution of transition metal ions. Therefore, the borate group, phenyl group and cyano group in the functional additive of the present application synergistically form a stable CEI film, effectively preventing the dissolution of transition metal ions and improving the high-temperature performance of the lithium ion battery.

[0028] In some preferred embodiments of the present application, the electrolyte additive can further include a sulfur-based additive, a carbonate-based additive, a silane-based additive and a lithium salt additive; wherein the mass ratio of the functional additive, the sulfur-based additive, the carbonate-based additive, the silane-based 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).

[0029] In some embodiments of the present application, the sulfur-based additive is ethylene sulfate (DTD), 1,3-propane sultone (PS) or methylene methane disulfonate (MMDS).

[0030] The sulfur-based additive can form a dense and stable SEI film on the surface of the negative electrode, 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 additive can also form a CEI film on the surface of the positive electrode to prevent corrosion of the positive electrode material and excessive decomposition of the electrolyte.

[0031] In some embodiments of the present application, the carbonate additive is ethylene carbonate (VC). VC is an unsaturated compound, which is easy to get electrons and is reduced on the negative electrode. After the carbonate additive is added to the electrolyte, it is preferentially reduced on the negative electrode during formation and participates in the formation of the SEI film. The VC forms a high-polymer-content SEI film on the negative electrode, which has good wettability and is beneficial to the retention of electrolyte on the negative electrode SEI film, reducing the negative effects of local dryness of electrolyte.

[0032] In some embodiments of the present application, the silane additive is tetraethylenesilane (TVSi) or vinyltrimethylsilane.

[0033] The silane additive has the ability to coordinate with lithium ions, can participate in the solvation shell of lithium ions, and is reduced and decomposed on the electrode surface during the migration of lithium ions, thereby obtaining an SEI film rich in inorganic lithium salt, regulating the composition of the electrode interface, improving the transmission performance of lithium ions, and improving the rate performance of lithium ion batteries. The silane additive can also reduce the gas generation behavior of high-nickel materials at high temperatures.

[0034] In some embodiments of the present application, the lithium salt additive is lithium difluorophosphate (LiPO2F2), lithium bisfluorosulfonylimide, lithium bis(oxalato)borate (LiBOB), or lithium bis(fluorooxalato)borate (LiODFB).

[0035] The lithium salt additive mainly functions to decompose and form a film on the positive and negative electrodes, has good film density, and reduces the impedance of the lithium ion battery.

[0036] Based on the electrolyte additive described above, the present application provides an electrolyte, which comprises an organic solvent, a lithium salt, and an electrolyte additive.

[0037] The organic solvent comprises a cyclic carbonate and a chain carbonate, wherein the cyclic carbonate comprises fluoroethylene carbonate and ethylene carbonate, and the chain carbonate comprises dimethyl carbonate and methyl ethyl carbonate.

[0038] In some embodiments of the present application, 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).

[0039] In some embodiments of the present application, the lithium salt is lithium hexafluorophosphate (LiPF6), the mass percentage of the lithium salt in the electrolyte is 11%-16%, and the mass percentage of the electrolyte additive is 0.3%-4%.

[0040] Example 1 The electrolyte used in this example has the following formulation in terms of mass percent of components: 0.3% functional additive (compound of formula I-1, 3-methyl-4-cyanophenyl boronic acid pinacol ester), 14% LiPF6, and the balance organic solvent. The organic solvent in the above electrolyte formulation consists of vinylene fluoride, vinyl ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, wherein the volume percent of vinylene fluoride is 2%, the volume percent of vinyl ethylene carbonate is 20%, the volume percent of dimethyl carbonate is 60%, and the volume percent of ethyl methyl carbonate is 18%, based on 100% of the total volume of the organic solvent.

[0041]

[0042] Example 2 The electrolyte used in this example has the following formulation in terms of mass percent of components: 0.5% functional additive (compound of formula I-1, 3-methyl-4-cyanophenyl boronic acid pinacol ester), 14% LiPF6, and the balance organic solvent. The organic solvent in the above electrolyte formulation consists of vinylene fluoride, vinyl ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, wherein the volume percent of vinylene fluoride is 2%, the volume percent of vinyl ethylene carbonate is 20%, the volume percent of dimethyl carbonate is 60%, and the volume percent of ethyl methyl carbonate is 18%, based on 100% of the total volume of the organic solvent.

[0043] Example 3 The electrolyte used in this example has the following formulation in terms of mass percent of components: 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 organic solvent. The organic solvent in the above electrolyte formulation consists of vinylene fluoride, vinyl ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, wherein the volume percent of vinylene fluoride is 2%, the volume percent of vinyl ethylene carbonate is 20%, the volume percent of dimethyl carbonate is 60%, and the volume percent of ethyl methyl carbonate is 18%, based on 100% of the total volume of the organic solvent.

[0044] Example 4 This example provides an electrolyte which differs from Example 3 only in that the functional additive in the electrolyte is compound of formula I-2 (4-cyanobiphenyl-4-boronic acid pinacol ester), and other conditions are the same as in Example 3.

[0045]

[0046] Example 5 The present example provides an electrolyte, which is different from example 3 only in that the functional additive in the electrolyte is a compound of formula I-3 (2-cyano-3-fluorophenyl boronic acid pinacol ester), and other conditions are the same as example 3.

[0047]

[0048] Example 6 The present example provides an electrolyte, which is different from example 3 only in that the amount of sulfur-containing additive PS is adjusted to 1%, and other conditions are the same as example 3.

[0049] Example 7 The present example provides an electrolyte, which is different from example 3 only in that the sulfur-containing additive PS is replaced by DTD, and the amount of addition is 1.5%, and other conditions are the same as example 3.

[0050] Example 8 The present example provides an electrolyte, which is different from example 3 only in that the sulfur-containing additive PS is replaced by MMDS, and other conditions are the same as example 3.

[0051] Example 9 The present example provides an electrolyte, which is different from example 3 only in that the amount of VC in example 3 is adjusted to 0.5%, and other conditions are the same as example 3.

[0052] Example 10 The present example provides an electrolyte, which is different from example 3 only in that the TVSi in example 3 is replaced by allyl trimethylsilane, and the amount of addition is 0.5%, and other conditions are the same as example 3.

[0053] Example 11 The present example provides an electrolyte, which is different from example 3 only in that the amount of LiPF6 in example 3 is adjusted to 12%, and other conditions are the same as example 3.

[0054] Example 12 The present example provides an electrolyte, which is different from example 3 only in that the amount of LiPF6 in example 3 is adjusted to 15%, and other conditions are the same as example 3.

[0055] Example 13 The present example provides an electrolyte, which is different from example 3 only in that the LiBOB in example 3 is replaced by LiPO2F2, and other conditions are the same as example 3.

[0056] Example 14 This example provides an electrolyte, which is only different from example 3 in that LiBOB in example 3 is replaced by LiODFB, and other conditions are the same as example 3.

[0057] Comparative Example 1 This comparative example provides an electrolyte, which is only different from example 1 in that the functional additive of formula I-1 is not contained in the electrolyte, and an additive of formula I-4 is added, and the difference between the functional additive in example 1 is that the additive of formula I-4 does not contain a cyano group.

[0058]

[0059] Comparative Example 2 This comparative example provides an electrolyte, which is only different from example 1 in that the functional additive of formula I-1 is not contained in the electrolyte, and an additive of formula I-5 is added, and the difference between the functional additive in example 1 is that the additive of formula I-5 does not contain a borate group.

[0060]

[0061] Comparative Example 3 This comparative example provides an electrolyte, which is only different from example 3 in that the functional additive is not contained in the electrolyte, and other conditions are the same as example 3.

[0062] Lithium ion battery assembly: graphite is used as negative active material, graphite, conductive agent acetylene black, binder carboxymethyl cellulose (Carboxylmethyl Cellulose, CMC), styrene-butadiene rubber (Styrene-Butadiene Rubber, SBR) are prepared into negative electrode slurry according to the mass ratio of 95.4:1.5:1.4:1.7, the negative electrode slurry is coated on the copper foil current collector, vacuum dried, and the negative electrode sheet is prepared; NCM811 is used as positive active material, the positive active material, conductive agent acetylene black, binder polyvinylidene fluoride (Polyvinylidene Fluoride, PVDF) are prepared into positive electrode slurry according to the mass ratio of 96.5:2.2:1.3, the positive electrode slurry is coated on the aluminum foil current collector, vacuum dried, and the positive electrode sheet is prepared; the electrolyte prepared in the example and the comparative example is assembled into a lithium ion battery with the above positive electrode sheet, negative electrode sheet and separator.

[0063] Among them, NCM811 is a typical type of ternary lithium ion battery positive material, belonging to lithium nickel cobalt manganese oxide (LiNi x Co y Mn z O)system.

[0064] The assembled lithium ion battery is tested for electrical performance as follows: (1) High temperature cycle performance test At 45℃, the lithium ion battery was charged at 1C (nominal capacity) constant current to 4.25V, then charged at 4.25V constant voltage to current ≤0.05C, and after 10min, discharged at 1C constant current to cut-off voltage 2.8V, the above was one charge-discharge cycle. The lithium ion battery was subjected to 350 charge-discharge cycles at 45℃ according to the above conditions, the capacity retention rate was calculated according to the following formula, and the results were shown in Table 1. Figure 1 .

[0065] Capacity retention rate of lithium ion battery after N cycles (%) = (discharge capacity of the Nth cycle / first discharge capacity) x 100% Wherein, N is the number of charge-discharge cycles.

[0066] (2) High temperature storage performance test of lithium ion battery The lithium ion battery was charged at 1C (nominal capacity) constant current to 4.25V, then charged at 4.25V constant voltage to current ≤0.05C, and after 10min, discharged at 1C constant current to 2.8V, the above was one charge-discharge cycle. The lithium ion battery was subjected to 3 charge-discharge cycles at 25℃ at 1C charge-discharge rate, then charged to full capacity at 1C rate, and the capacity Q0 of the lithium ion battery was recorded. The lithium ion battery in full capacity 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 1C rate for 2 weeks at 25℃, and the 1C discharge capacity Q2 was recorded, the high temperature storage capacity retention rate and capacity recovery rate of the lithium ion battery were calculated, and the experimental data were shown in Table 2. Figure 2 . The calculation formula used was as follows: Capacity retention rate (%) = Q1 / Q0 x 100% Capacity recovery rate (%) = Q2 / Q0 x 100% Combined with Figure 1 and Figure 2Compared with Comparative Example 1 and Comparative Examples 1-2, the electrolyte of Example 1 can significantly improve the high-temperature storage performance and high-temperature cycle performance of the lithium ion battery by introducing the functional additive shown as Formula I-1. This is mainly because the functional additive introduced in the application contains borate groups, phenyl groups and cyano groups, and the synergistic effect of the three functional groups significantly improves the high-temperature performance of the lithium ion battery. Although the additive of Comparative Example 1 also contains borate groups and phenyl groups, it does not contain cyano groups, so the positive electrode film forming quality is not good, which leads to poor high-temperature performance of the corresponding lithium ion battery; the additive of Comparative Example 2 does not contain borate groups, and the film forming quality is not as good as the functional additive in Example 1, so the high-temperature performance of the corresponding lithium ion battery is not as good as that of the lithium ion battery corresponding to Example 1. The electrolyte of Comparative Example 3 does not contain an additive, so the high-temperature storage performance and high-temperature cycle performance of the lithium ion battery are weaker than those of the lithium ion batteries corresponding to Comparative Examples 1 and 2.

[0067] From Figure 1 It can be seen that compared with Example 1, the high-temperature cycle performance of the lithium ion battery obtained by increasing the amount of functional additive in Example 2 is improved, which further proves the improvement effect of the functional additive on the high-temperature cycle performance of the lithium ion battery. Compared with Example 2, the high-temperature cycle performance of the lithium ion battery is further improved by further adding other additives in Example 3. In addition, compared with Example 3, when the compound of Formula I-2 is used as the functional additive in Example 4, the high-temperature cycle performance of the lithium ion battery is further improved, because the number of phenyl groups in the compound of Formula I-2 is more than that in the compound of Formula I-1, which further illustrates the role of phenyl groups in the functional additive in improving the high-temperature cycle performance of the lithium ion battery. Compared with Example 3, the high-temperature cycle performance of the lithium ion battery is more excellent when the sulfur-based additives DTD and MMDS are used in Examples 7 and 8, respectively. From the performance data of Example 10, it can be seen that allyl trimethylsilane can more significantly improve the high-temperature cycle performance of the lithium ion battery than TVSi. Compared with Example 3, Example 11 and Example 12, it can be seen that when the mass fraction of lithium salt is 12%, the high-temperature cycle performance of the lithium ion battery is optimal.

[0068] From Figure 3 It can be seen that the electrochemical window of the electrolyte composed of 0.3% of the functional additive of Example 1, lithium salt and organic solvent reaches 4.7V, which indicates that the electrolyte has strong resistance to oxidation and reduction reactions and will not easily decompose or undergo other irreversible electrochemical reactions within a wide voltage range, and can maintain stable chemical properties.

[0069] In summary, the functional additive having the structural formula of Formula I in the application is not the independent action of a single functional group, but the synergistic effect of the whole structure in the electrolyte, and this synergistic effect is the key to improving the performance and stability of the lithium ion battery.

[0070] It should be pointed out finally that the above embodiments are only used to illustrate the technical solutions of the present application but not to limit it. Although the present application has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that the specific embodiments of the present application can be modified or equivalently replaced without departing from the spirit and scope of the present application, and any modification or equivalent replacement should be covered in the protection scope of the claims of the present application.

Claims

1. An electrolyte additive, characterized in that Including functional additives, the structural formula of the functional additives is shown in Formula I: wherein R1, R2, R3, R4 and R5 are 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 cyano.

2. The electrolyte additive according to claim 1, characterized in that The functional additive is one of the following compounds: 。 3. The electrolyte additive according to claim 1, characterized in that The electrolyte additives further include sulfur additives, carbonate additives, silane additives and lithium salt additives, and the mass ratio of the functional additives, sulfur 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).

4. The electrolyte additive according to claim 3, characterized in that The sulfur additive is vinyl sulfate, 1,3-propane sultone or methylene methanedisulfonate.

5. The electrolyte additive according to claim 3, characterized in that The carbonate additive is ethylene carbonate.

6. The electrolyte additive according to claim 3, characterized in that The silane additive is tetravinylsilane or vinyltrimethylsilane.

7. The electrolyte additive according to claim 3, characterized in that The lithium salt additive is lithium difluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(oxalatoborate) or lithium bis(fluorooxalatoborate).

8. An electrolyte, characterized in that The electrolyte comprises an organic solvent, a lithium salt and the electrolyte additive according to any one of claims 1 to 7.

9. The electrolyte according to claim 8, characterized in that The lithium salt is lithium hexafluorophosphate.

10. A lithium ion battery, characterized in that: Comprising the electrolyte according to claim 8.

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