Electrolyte, preparation method thereof and lithium ion battery
By using organic small molecules containing C=C bonds as additives in the lithium-ion battery electrolyte solution, an excellent SEI film is formed, which solves the problems of complex structure, high cost and high toxicity of additives in the prior art, and realizes the high cycle performance of lithium-ion batteries and the feasibility of industrial production.
Patent Information
- Application Number
- CN202510257816.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-05
- Publication Date
- 2025-06-06
AI Technical Summary
The new additives in existing lithium-ion battery electrolytes have complex structure, high cost and high toxicity, resulting in poor performance of SEI membranes and difficult to industrially produce.
The organic small molecules containing C=C bonds are used as additives for the electrolyte, which can undergo a reduction polymerization reaction on the surface of the graphite electrode to form an elastic polymer framework, thereby forming a uniform, stable, thin and dense SEI film. At the same time, the phosphate groups, sulfonic acid groups and boric acid groups in the additive promote the formation of SEI films rich in inorganic components such as lithium phosphate, lithium sulfonate and lithium boricate.
By forming an excellent SEI film, the continuous decomposition of organic solvents and lithium salts is effectively suppressed, the graphite electrode structure is protected, the interface impedance is reduced, and the circulation performance of lithium-ion batteries is improved. In addition, additives have the advantages of simple structure, stable properties, easy industrial production and low cost.
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Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to an electrolyte and a preparation method thereof, and a lithium ion battery. Background Art
[0002] Lithium-ion batteries have the advantages of small size, light weight, high energy density and high conversion efficiency, and are considered to be one of the most promising advanced energy storage devices. Graphite is the most commonly used negative electrode material on the market, with the advantages of low cost, low lithium insertion potential and high theoretical specific capacity. A series of interfacial side reactions will occur in the graphite electrode during contact with the electrolyte to form an SEI film. The SEI film formed during the first charge and discharge process is often unstable, and some solvent co-intercalation will produce gas and uneven sediments, thereby destroying the layered structure of graphite. In addition, graphite will produce a certain degree of volume expansion during the lithium insertion process, causing the SEI film to rupture, exposing new active sites, causing the electrolyte to continue to undergo reduction and decomposition reactions, generating new SEI films, and resulting in continuous loss of active lithium. At the same time, the thickening of the SEI film and the increase in interfacial impedance will affect the transmission of lithium ions at the interface, ultimately leading to capacity decay of lithium-ion batteries and even battery failure.
[0003] Introducing film-forming additives into the electrolyte to decompose them in situ during the cycle to form a good SEI film is a simple and quick method. However, the current new electrolyte additives have problems such as low solubility, complex structure, high cost and high toxicity, which make it impossible to achieve industrial production. Summary of the invention
[0004] The main purpose of the present invention is to provide an electrolyte and a preparation method thereof, and a lithium-ion battery, so as to solve the problem that the new additives in the electrolyte in the prior art have complex structure, high cost and high toxicity, resulting in poor SEI film performance and difficulty in industrial production.
[0005] In order to achieve the above object, according to one aspect of the present invention, an electrolyte is provided, comprising an additive, a lithium salt and an organic solvent; the chemical structure of the additive is generally: Wherein, R1 and R2 are each independently selected from hydrogen or methyl, and R3 is selected from any one of phosphate, sulfonate and borate.
[0006] Furthermore, the additive is selected from any one or more of 2,2-dimethylvinylboronic acid, vinylphosphoric acid, vinylsulfonic acid and allylsulfonic acid; the additive also includes fluoroethylene carbonate, and preferably the additive is a combination of 2,2-dimethylvinylboronic acid and fluoroethylene carbonate, and the mass ratio of 2,2-dimethylvinylboronic acid to fluoroethylene carbonate is 0.01-5:1-8.
[0007] Furthermore, the mass proportion of the additive in the electrolyte is 0.01-5%, and / or the mass ratio of the additive to the lithium salt is 0.01-5:5-25.
[0008] Further, the lithium salt is selected from any one or more of lithium hexafluorophosphate, lithium difluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium bis(trifluoromethylsulfonyl)imide and lithium bis(fluorosulfonyl)imide, and / or the molar concentration of the lithium salt in the electrolyte is 0.5 to 2 mol / L.
[0009] Furthermore, the organic solvent is selected from any one or more of ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propylene carbonate and fluoroethylene carbonate; preferably, the organic solvent is a combination of ethylene carbonate and dimethyl carbonate, and the volume ratio of ethylene carbonate to dimethyl carbonate is 1 to 5:1.
[0010] According to another aspect of the present invention, a method for preparing the above-mentioned electrolyte is provided, the preparation method comprising: mixing raw materials including additives, lithium salts and organic solvents to obtain an electrolyte; the chemical structure of the additive is generally: Wherein, R1 and R2 are each independently selected from hydrogen or methyl, and R3 is selected from any one of phosphate, sulfonate and borate.
[0011] Furthermore, the preparation method further includes: step S1, mixing raw materials including additives and organic solvents to obtain a first mixed liquid; step S2, sequentially mixing and first allowing to stand raw materials including the first mixed liquid and molecular sieves to obtain a second mixed liquid; step S3, removing the molecular sieves in the second mixed liquid to obtain a third mixed liquid; and step S4, sequentially mixing and second allowing to stand raw materials including the third mixed liquid and lithium salts to obtain an electrolyte.
[0012] Furthermore, in the above step S2, the first standing time is 24 to 72 hours; and / or, the molecular sieve is selected from any one or more of potassium A-type molecular sieve, sodium A-type molecular sieve and calcium A-type molecular sieve; and / or, the mass ratio of the first mixed liquid to the molecular sieve is 1 to 2:2 to 4.
[0013] Furthermore, in the above step S4, the second standing time is 24 to 72 hours.
[0014] According to another aspect of the present invention, there is provided a lithium-ion battery, comprising a positive electrode, a negative electrode and an electrolyte, wherein the electrolyte is the electrolyte described above.
[0015] Applying the technical solution of the present invention, the present application uses the organic small molecules of the above chemical structure containing C=C bonds as additives to the electrolyte. The C=C bonds enable the additives to preferentially undergo reduction polymerization reactions on the surface of the graphite electrode to generate a polymer skeleton with elasticity, thereby forming a uniform, stable, thin and dense SEI film, thereby effectively inhibiting the continuous decomposition of organic solvents and lithium salts and protecting the graphite electrode structure from being destroyed. At the same time, the phosphate group, sulfonic acid group and boric acid group in the additive can promote the formation of an SEI film rich in inorganic components such as lithium phosphate, lithium sulfonate and lithium borate, thereby facilitating the formation of a fast channel for lithium ion transmission, effectively reducing the interface impedance, and thereby improving the cycle performance of lithium ion batteries. In addition, the additives of the present application have the advantages of simple structure, stable properties, easy industrial production and low cost. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:
[0017] Figure 1 A comparison chart of the cycle performance of lithium-ion batteries prepared using the electrolytes of Example 3 and Comparative Example 1 of the present application is shown. DETAILED DESCRIPTION
[0018] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.
[0019] As analyzed in the background technology of this application, in the prior art, new additives in the electrolyte have the problems of complex structure, high cost and high toxicity, resulting in poor SEI film performance and difficulty in industrial production. In order to solve the above problems, this application provides an electrolyte and a preparation method thereof, and a lithium-ion battery.
[0020] In a typical embodiment of the present application, an electrolyte is provided, comprising an additive, a lithium salt and an organic solvent; the chemical structure of the additive is generally: Wherein, R1 and R2 are each independently selected from hydrogen or methyl, and R3 is selected from any one of phosphate, sulfonate and borate.
[0021] The present application uses small organic molecules with the above chemical structure containing C=C bonds as additives to the electrolyte. The C=C bonds enable the additives to preferentially undergo reduction polymerization reactions on the surface of the graphite electrode to generate a polymer skeleton with elasticity, thereby forming a uniform, stable, thin and dense SEI film, thereby effectively inhibiting the continuous decomposition of organic solvents and lithium salts and protecting the graphite electrode structure from being destroyed. At the same time, the phosphate group, sulfonic acid group and boric acid group in the additive can promote the formation of an SEI film rich in inorganic components such as lithium phosphate, lithium sulfonate and lithium borate, thereby facilitating the formation of a fast channel for lithium ion transmission, effectively reducing the interface impedance, and thereby improving the cycle performance of lithium-ion batteries. In addition, the additives of the present application have the advantages of simple structure, good solubility, stable properties, non-toxicity, easy industrial production and low cost.
[0022] In order to further improve the cycle performance of lithium-ion batteries, in one embodiment of the present application, the additive is selected from any one or more of 2,2-dimethylvinylboronic acid, vinylphosphoric acid, vinylsulfonic acid and allylsulfonic acid; the additive also includes fluoroethylene carbonate, and preferably the additive is a combination of 2,2-dimethylvinylboronic acid and fluoroethylene carbonate, and the mass ratio of 2,2-dimethylvinylboronic acid to fluoroethylene carbonate is 0.01~5:1~8.
[0023] The preferred additive also includes fluoroethylene carbonate, and preferably a combination of 2,2-dimethylvinylboronic acid and fluoroethylene carbonate, and the mass ratio of the two is controlled within the above range, which helps to improve the performance of the SEI film and reduce the interface impedance, thereby further improving the cycle stability and discharge specific capacity of the battery.
[0024] In one embodiment of the present application, the mass ratio of the additive in the electrolyte is 0.01-5%, and / or the mass ratio of the additive to the lithium salt is 0.01-5:5-25.
[0025] The mass ratio of the additive in the electrolyte is preferably within the above range, which helps to preferentially cause reduction polymerization on the surface of the graphite electrode to generate an elastic polymer skeleton, thereby better forming a uniform, stable, thin and dense SEI film. The mass ratio of the additive to the lithium salt is preferably within the above range, which helps to improve the electrochemical stability of the electrolyte.
[0026] In one embodiment of the present application, the lithium salt is selected from any one or more of lithium hexafluorophosphate, lithium difluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium bis(trifluoromethylsulfonyl)imide and lithium bis(fluorosulfonyl)imide, and / or the molar concentration of the lithium salt in the electrolyte is 0.5 to 2 mol / L.
[0027] In one embodiment of the present application, the organic solvent is selected from any one or more of ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propylene carbonate and fluoroethylene carbonate; preferably, the organic solvent is a combination of ethylene carbonate and dimethyl carbonate, and the volume ratio of ethylene carbonate to dimethyl carbonate is 1 to 5:1.
[0028] The type of the organic solvent is preferably within the above range, which helps dissolve the lithium salt, thereby providing sufficient lithium ions. The organic solvent is preferably a combination of ethylene carbonate and dimethyl carbonate, and the volume ratio of the two is controlled within the above range, which helps to better dissolve the lithium salt and additives, thereby making the electrolyte have good conductivity.
[0029] In another typical embodiment of the present application, a method for preparing the above-mentioned electrolyte is provided, the preparation method comprising: mixing raw materials including additives, lithium salts and organic solvents to obtain an electrolyte; the chemical structure of the additive is generally: Wherein, R1 and R2 are each independently selected from hydrogen or methyl, and R3 is selected from any one of phosphate, sulfonate and borate.
[0030] The electrolyte prepared by the above method, by adding the additive of the above chemical structure to the raw material, can preferentially undergo reduction polymerization reaction on the surface of the graphite electrode to generate a polymer skeleton with elasticity, thereby forming a uniform, stable, thin and dense SEI film, and the SEI film is rich in inorganic components such as lithium phosphate, lithium sulfonate and lithium borate, which can effectively inhibit the continuous decomposition of organic solvents and lithium salts, protect the graphite electrode structure from being destroyed and effectively reduce the interface impedance, thereby improving the cycle performance of lithium ion batteries. In addition, the preparation method of the present application is simple and the production cost is low.
[0031] In one embodiment of the present application, the preparation method further includes: step S1, mixing raw materials including additives and organic solvents to obtain a first mixed liquid; step S2, sequentially mixing and first standing the raw materials including the first mixed liquid and molecular sieves to obtain a second mixed liquid; step S3, removing the molecular sieves in the second mixed liquid to obtain a third mixed liquid; and step S4, sequentially mixing and second standing the raw materials including the third mixed liquid and lithium salts to obtain an electrolyte.
[0032] The above step S1 helps the additive to be fully dissolved in the organic solvent. The use of molecular sieves helps to remove trace moisture in the additive, thereby reducing the hydrolysis of lithium salts, thereby improving the stability and safety of the electrolyte. The last added lithium salt helps to fully dissolve the lithium salt, thereby providing sufficient lithium ions, thereby improving the conductivity of the electrolyte.
[0033] In one embodiment of the present application, in the above step S2, the first standing time is 24 to 72 hours; and / or, the molecular sieve is selected from any one or more of potassium A-type molecular sieve, sodium A-type molecular sieve and calcium A-type molecular sieve; and / or, the mass ratio of the first mixed liquid to the molecular sieve is 1 to 2:2 to 4.
[0034] The type of molecular sieve, the mass ratio of the first mixed liquid to the molecular sieve and the first standing time are preferably within the above ranges, which helps to improve the effect of the molecular sieve in removing trace moisture in the additive, thereby further reducing lithium salt hydrolysis, and further improving the stability and safety of the electrolyte.
[0035] In one embodiment of the present application, in the above step S4, the second standing time is 24 to 72 hours.
[0036] It is preferred to control the second standing time within the above range, which helps to improve the stability and uniformity of the electrolyte.
[0037] In another typical embodiment of the present application, a lithium-ion battery is provided, comprising a positive electrode, a negative electrode and an electrolyte, wherein the electrolyte is the electrolyte described above.
[0038] The lithium-ion battery comprising the above electrolyte has good cycle performance.
[0039] The beneficial effects of the present application will be further illustrated below in conjunction with embodiments.
[0040] Example 1
[0041] Preparation of organic solvent: In an argon-filled glove box, ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed at a volume ratio of 1:1 to obtain EC:DMC organic solvent.
[0042] Add the additive 2,2-dimethylvinylboronic acid (DEBA) to 2 mL of EC:DMC organic solvent and stir to dissolve to obtain a first mixed solution. Add 4 g of potassium A-type molecular sieve to the first mixed solution and let it stand for 24 hours to remove water to obtain a second mixed solution. Remove the molecular sieve in the second mixed solution to obtain a third mixed solution. Add 0.3 g of 1 mol / L lithium salt lithium hexafluorophosphate (LiPF 6 ), mixed evenly and then allowed to stand for 24 hours to obtain an electrolyte. The additive 2,2-dimethylvinylboronic acid (DEBA) accounts for 0.01% by weight in the electrolyte.
[0043] Example 2
[0044] The difference from Example 1 is that the mass proportion of the additive 2,2-dimethylvinylboronic acid (DEBA) in the electrolyte is 0.5%, and the electrolyte is finally obtained.
[0045] Example 3
[0046] The difference from Example 1 is that the mass proportion of the additive 2,2-dimethylvinylboric acid (DEBA) in the electrolyte is 1%, and the electrolyte is finally obtained.
[0047] Example 4
[0048] The difference from Example 1 is that the mass proportion of the additive 2,2-dimethylvinylboric acid (DEBA) in the electrolyte is 5%, and the electrolyte is finally obtained.
[0049] Example 5
[0050] The difference from Example 1 is that the additive is vinyl phosphoric acid (VPA), and the mass proportion of the additive vinyl phosphoric acid (VPA) in the electrolyte is 0.5%, and finally an electrolyte is obtained.
[0051] Example 6
[0052] The difference from Example 1 is that the additive is vinyl phosphoric acid (VPA), and the mass proportion of the additive vinyl phosphoric acid (VPA) in the electrolyte is 1%, and finally an electrolyte is obtained.
[0053] Example 7
[0054] The difference from Example 1 is that the additive is vinyl sulfonic acid (VSA), and the mass proportion of the additive vinyl sulfonic acid (VSA) in the electrolyte is 0.5%, and an electrolyte is finally obtained.
[0055] Example 8
[0056] The difference from Example 1 is that the additive is vinyl sulfonic acid (VSA), and the mass proportion of the additive vinyl sulfonic acid (VSA) in the electrolyte is 1%, and an electrolyte is finally obtained.
[0057] Example 9
[0058] The difference from Example 4 is that the additive is a combination of 2,2-dimethylvinylboronic acid (DEBA) and fluoroethylene carbonate (FEC), the mass ratio of 2,2-dimethylvinylboronic acid (DEBA) to fluoroethylene carbonate (FEC) is 1:5, and finally an electrolyte is obtained.
[0059] Example 10
[0060] The difference from Example 4 is that the additive is a combination of 2,2-dimethylvinylboronic acid (DEBA) and fluoroethylene carbonate (FEC), the mass ratio of 2,2-dimethylvinylboronic acid (DEBA) to fluoroethylene carbonate (FEC) is 1:10, and an electrolyte is finally obtained.
[0061] Embodiment 11
[0062] The difference from Example 1 is that the additive 2,2-dimethylvinylboronic acid (DEBA) accounts for 6% by mass in the electrolyte, and an electrolyte is finally obtained.
[0063] Example 12
[0064] The difference from Example 1 is that the mass ratio of the additive 2,2-dimethylvinylboric acid and the lithium salt lithium hexafluorophosphate is 0.01:23, the molar concentration of lithium hexafluorophosphate is 2 mol / L, and finally an electrolyte is obtained.
[0065] Example 13
[0066] The difference from Example 1 is that the mass ratio of the additive 2,2-dimethylvinylboric acid and the lithium salt lithium hexafluorophosphate is 0.01:31, the molar concentration of lithium hexafluorophosphate is 3 mol / L, and finally an electrolyte is obtained.
[0067] Comparative Example 1
[0068] The difference from Example 1 is that 1 mol / L lithium hexafluorophosphate is added to the EC:DMC organic solvent and the mixture is mixed evenly to obtain an electrolyte.
[0069] Comparative Example 2
[0070] The difference from Example 9 is that the additive is fluoroethylene carbonate, and an electrolyte is finally obtained.
[0071] Test method:
[0072] The electrolytes of the above examples and comparative examples were used to assemble Li / graphite 2032 button cells, and the charge-discharge cycle performance of the cells was tested at room temperature 25°C, 0.01V-2V and 0.2C rate. The specific steps are as follows:
[0073] Preparation of graphite electrode: Graphite, conductive carbon black and PVDF were dispersed evenly in N-methylpyrrolidone (NMP) at a mass ratio of 8:1:1. The slurry was evenly coated on copper foil using a scraper (100 μm) and dried in a vacuum oven at 120°C for 24 h. The dried electrode was cut into discs with a diameter of 12 mm to obtain graphite electrode.
[0074] Battery assembly: Using metal lithium sheets as counter electrodes and reference electrodes, 2032 button cells were assembled in an argon-filled glove box, and the electrolytes used in the above embodiment and comparative example were used. After assembly, a battery sealer was used to seal the cells, and the cells were left to stand for 4 hours to allow the electrolyte to fully infiltrate the positive and negative electrodes.
[0075] Electrochemical performance test: The battery was charged and discharged using the Land CT2001A tester from Wuhan Landian Company. The constant current charge and discharge test conditions were: at room temperature of 25°C, first activated three times with a small current of 0.05C, then a long cycle with a current of 0.2C, and the charge and discharge voltage range was 0.01V to 2V. After 100 charge and discharge cycles, the capacity retention rate and specific capacity of the 100th cycle were calculated, and the test results are shown in Table 1.
[0076] Table 1
[0077]
[0078] in, Figure 1 is a comparison chart of the cycle performance of lithium ion batteries prepared by the electrolytes of Example 3 and Comparative Example 1, Figure 1 It can be seen that the Li / graphite 2032 button batteries prepared by the electrolytes of Example 3 and Comparative Example 1 respectively, the battery of Example 3 has an initial discharge capacity of 343.2 mAh / g at a current of 0.2C, and after 100 cycles, the discharge capacity is 341.5 mAh / g; the battery of Comparative Example 1 has an initial discharge capacity of 312.8 mAh / g at 0.2C, and after 100 cycles, the discharge capacity is 288.4 mAh / g, indicating that the battery of Example 3 has good cycle stability. As can be seen from Table 1, the capacity retention rate of the battery of Example 3 is 99.5%, which is higher than the capacity retention rate of the battery of Comparative Example 1 (92.2%). In summary, it is shown that adding the additives of the embodiments of the present application can significantly improve the cycle stability and discharge capacity of the battery.
[0079] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:
[0080] The present application uses small organic molecules with the above chemical structure containing C=C bonds as additives to the electrolyte. The C=C bonds enable the additives to preferentially undergo reduction polymerization reactions on the surface of the graphite electrode to generate a polymer skeleton with elasticity, thereby forming a uniform, stable, thin and dense SEI film, thereby effectively inhibiting the continuous decomposition of organic solvents and lithium salts and protecting the graphite electrode structure from being destroyed. At the same time, the phosphate group, sulfonic acid group and boric acid group in the additive can promote the formation of an SEI film rich in inorganic components such as lithium phosphate, lithium sulfonate and lithium borate, thereby facilitating the formation of a fast channel for lithium ion transmission, effectively reducing the interface impedance, and thereby improving the cycle performance of lithium-ion batteries. In addition, the additives of the present application have the advantages of simple structure, stable properties, easy industrial production and low cost.
[0081] The above are only embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.
Claims
1. An electrolyte comprising an additive, a lithium salt and an organic solvent; characterized in that: The chemical structure formula of the additive is: Wherein, R1 and R2 are each independently selected from hydrogen or methyl, and R3 is selected from any one of phosphate, sulfonate and borate.
2. The electrolyte according to claim 1, characterized in that The additive is selected from any one or more of 2,2-dimethylvinylboronic acid, vinylphosphoric acid, vinylsulfonic acid and allylsulfonic acid; The additive further includes fluoroethylene carbonate. Preferably, the additive is a combination of 2,2-dimethylvinylboronic acid and fluoroethylene carbonate, and the mass ratio of the 2,2-dimethylvinylboronic acid to the fluoroethylene carbonate is 0.01-5:1-8.
3. The electrolyte according to claim 1 or 2, characterized in that The mass proportion of the additive in the electrolyte is 0.01-5%, and / or the mass ratio of the additive to the lithium salt is 0.01-5:5-25.
4. The electrolyte according to any one of claims 1 to 3, characterized in that The lithium salt is selected from any one or more of lithium hexafluorophosphate, lithium difluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium bis(trifluoromethylsulfonyl)imide and lithium bis(fluorosulfonyl)imide, and / or the molar concentration of the lithium salt in the electrolyte is 0.5 to 2 mol / L.
5. The electrolyte according to any one of claims 1 to 4, characterized in that The organic solvent is selected from any one or more of ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propylene carbonate and fluoroethylene carbonate; Preferably, the organic solvent is a combination of ethylene carbonate and dimethyl carbonate, and the volume ratio of the ethylene carbonate to the dimethyl carbonate is 1 to 5:
1.
6. A method for preparing the electrolyte according to any one of claims 1 to 5, characterized in that: The preparation method comprises: mixing raw materials including additives, lithium salt and organic solvent to obtain the electrolyte; The chemical structure formula of the additive is: Wherein, R1 and R2 are each independently selected from hydrogen or methyl, and R3 is selected from any one of phosphate, sulfonate and borate.
7. The preparation method according to claim 6, characterized in that: The preparation method further comprises: Step S1, mixing the raw materials including the additive and the organic solvent to obtain a first mixed solution; Step S2, sequentially mixing and first standing the raw materials including the first mixed solution and the molecular sieve to obtain a second mixed solution; Step S3, removing the molecular sieve in the second mixed solution to obtain a third mixed solution; and Step S4, sequentially mixing the raw materials including the third mixed solution and the lithium salt and allowing to stand for a second time to obtain the electrolyte.
8. The preparation method according to claim 7, characterized in that: In step S2, the first standing time is 24 to 72 hours; and / or the molecular sieve is selected from any one or more of potassium A-type molecular sieve, sodium A-type molecular sieve and calcium A-type molecular sieve; and / or the mass ratio of the first mixed solution to the molecular sieve is 1 to 2:2 to 4.
9. The preparation method according to claim 7, characterized in that: In the step S4, the second standing time is 24 to 72 hours.
10. A lithium ion battery comprising a positive electrode, a negative electrode and an electrolyte, characterized in that: The electrolyte is the electrolyte according to any one of claims 1 to 5.