A lithium-ion battery

Abstract

The application discloses a lithium ion battery. The lithium ion battery comprises a positive electrode sheet, a negative electrode sheet, a diaphragm and an electrolyte; wherein the positive electrode sheet comprises a positive electrode active material, the positive electrode active material is lithium iron phosphate; the electrolyte comprises an ether solvent, the ether solvent comprises a fluorinated ether solvent and a non-fluorinated ether solvent; the fluorinated ether solvent is a compound shown in the following formula I; wherein R2 is C4 alkylene or C4 fluorinated alkylene, the number of fluorine atoms in R2 is m, m >= 0; R1 and R3 are each independently methyl or fluorinated methyl, and the total number of fluorine atoms in R1 and R3 is n, n >= 1; and m + n = 4. The lithium ion battery provided by the application has good high-temperature cycle performance and a wide electrochemical window.

Description

TECHNICAL FIELD

[0001] The present application relates to a lithium ion battery. BACKGROUND

[0002] The lithium iron phosphate battery is currently the mainstream of passenger car batteries. The intrinsic defects of the vehicle lithium iron phosphate battery in fast charging are large impedance and easy lithium precipitation of the negative electrode at large rate, which is one of the main reasons for limiting its further development in the market.

[0003] One solution in the prior art is to introduce natural graphite into the negative electrode. Natural graphite has high porosity, high graphitization degree and high compaction density, and is the most suitable large-capacity carbon negative electrode material for fast charging. It can also improve the overall energy density of the battery cell by its compaction and capacity advantages, thereby extending the endurance of the electric vehicle. However, natural graphite has not been used as a negative active material for high-kinetic lithium iron phosphate batteries because of its high chemical-electrochemical instability, which significantly reduces the initial efficiency of the battery and affects the cycle storage performance. The conventional method is to use more stable solvents and more negative electrode film-forming additives. However, both of these methods will significantly worsen ion conduction and battery DCR, thereby causing the battery cell to lose fast charging capability and shorten the calendar life.

[0004] To solve the problem of instability of the natural graphite negative electrode, one technical route is to use a reduction-resistant solvent such as dimethyl ether (DME), which cannot form a film on the negative electrode, thus avoiding the problem of large negative electrode impedance caused by the formation of a solid electrolyte layer. In addition, DME has poor solubility for lithium salts, low ionic conductivity, and poor oxidation resistance, making it difficult to maintain stability even in the lithium iron phosphate system. To solve the problem of oxidation resistance, the ether solvent can be modified, but this may greatly reduce the solubility of common lithium salts, making the electrolyte unusable.

[0005] Therefore, how to solve the above-mentioned defects is a very important research direction in the field of lithium ion batteries. SUMMARY

[0006] The present application is mainly to overcome the defects of low electrochemical window, low solubility of lithium salt and poor high-temperature cycle stability of the electrolyte of the lithium ion battery in the prior art, and provides a lithium ion battery. The lithium ion battery provided by the present application has good high-temperature cycle performance and a wide electrochemical window.

[0007] The lithium ion battery provided by the present application comprises a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte; wherein the positive electrode sheet comprises a positive electrode active material, and the positive electrode active material is lithium iron phosphate;

[0008] The electrolyte comprises an ether solvent, and the ether solvent comprises a fluorinated ether solvent and a non-fluorinated ether solvent; the fluorinated ether solvent is a compound represented by the following formula I:

[0009] Formula I,

[0010] wherein R2 is a C4 alkylene or a C4 fluoroalkylene, and the number of fluorine atoms in R2 is m, m≥0; R1 and R3 are each independently a methyl or a fluoromethyl, and the total number of fluorine atoms in R1 and R3 is n, n≥1; and m+n=4.

[0011] On the basis of common general knowledge in the art, the above-mentioned preferred conditions can be combined arbitrarily, thereby obtaining various preferred examples of the present application.

[0012] The reagents and raw materials used in the present application are commercially available.

[0013] The positive progress effect of the present application is that:

[0014] The present application can effectively broaden the electrochemical window of the electrolyte by involving the fluorinated ether solvent and the non-fluorinated ether solvent with specific structures in the electrolyte, and the high-temperature cycle performance of the obtained lithium ion battery is also improved, and further, the lithium ion battery also has good direct current impedance and low-temperature capacity retention rate. DETAILED DESCRIPTION

[0015] Lithium ion battery

[0016] The lithium ion battery provided by the present application comprises a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte; wherein the positive electrode sheet comprises a positive electrode active material, and the positive electrode active material is lithium iron phosphate;

[0017] The electrolyte comprises an ether solvent, and the ether solvent comprises a fluorinated ether solvent and a non-fluorinated ether solvent; the fluorinated ether solvent is a compound shown in the following Formula I:

[0018] Formula I,

[0019] wherein R2 is a C4 alkylene or a C4 fluoroalkylene, and the number of fluorine atoms in R2 is m, m≥0; R1 and R3 are each independently a methyl or a fluoromethyl, and the total number of fluorine atoms in R1 and R3 is n, n≥1; and m+n=4.

[0020] In the present application, the compound shown in Formula I can be selected from at least one of the following compounds:

[0021] , ,

[0022] , ,

[0023] and .

[0024] In the present application, the content of the ether solvent can be greater than 60wt%, the percentage being the mass percentage of the ether solvent in the mass of the electrolyte.

[0025] In the present application, the content of the fluorinated ether solvent is 10wt%-60wt%, the percentage being the mass percentage of the fluorinated ether solvent in the total mass of the ether solvent. Preferably, the content of the fluorinated ether solvent is 10wt%-50wt%, the percentage being the mass percentage of the fluorinated ether solvent in the total mass of the ether solvent.

[0026] In some specific embodiments, the content of the fluorinated ether solvent can be 5wt%, 10wt%, 20wt%, 50wt% or 60wt%, the percentage being the mass percentage of the fluorinated ether solvent in the total mass of the ether solvent.

[0027] In the present application, the non-fluorinated ether solvent can be one or more selected from dimethyl ether (DME), tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether.

[0028] In the present application, the additive can include vinylene carbonate (VC), and the content of the vinylene carbonate is preferably 0.2wt%-4wt%, the percentage being the mass percentage of the additive in the mass of the electrolyte.

[0029] In some specific embodiments, the additive is vinylene carbonate, and the content of the vinylene carbonate is 0.1wt%, 0.2wt%, 1wt%, 2wt%, 2.5wt%, 3wt%, 4wt% or 5wt%.

[0030] In the present application, the additive includes one or both of a sulfate and a sulfonate; the sulfate includes vinyl sulfate (DTD); the sulfonate is one or both of methylene methanedisulfonate (MMDS) and 1,3-propanesultone; and the content of the additive is preferably 0.1wt%-0.8wt%, the percentage being the mass percentage of the additive in the mass of the electrolyte.

[0031] In some specific embodiments, the additive is vinylene carbonate and vinyl sulfate, wherein the content of the vinylene carbonate is 2.5wt% and the content of the vinyl sulfate is 0.05wt%, 0.1wt%, 0.4wt%, 0.8wt% or 1wt%.

[0032] In some specific embodiments, the additives are vinylene carbonate and methyl methane disulfonate, wherein the content of vinylene carbonate is 2.5 wt% and the content of methyl methane disulfonate is 0.4 wt%.

[0033] In some specific embodiments, the additive is vinylene carbonate, vinyl sulfate, and methylene disulfonate, wherein the content of vinylene carbonate is 2.5 wt%, the content of vinyl sulfate is 0.2 wt%, and the content of methylene disulfonate is 0.2 wt%.

[0034] In this application, the mass ratio of vinylene carbonate to vinyl sulfate can be 1:(0.16-0.32).

[0035] In some specific embodiments, the mass ratio of vinylene carbonate to vinyl sulfate is 1:0.02, 1:0.04, 1:0.16, 1:0.32, or 1:0.4.

[0036] In this application, the electrolyte may further include ethylene carbonate.

[0037] In some specific embodiments, the mass ratio of the ethylene carbonate to the ether solvent is 2:8 or 3:7.

[0038] In this application, the negative electrode sheet includes a negative electrode active material, which may be natural graphite.

[0039] Preferably, the graphitization degree of the natural graphite is 94%-98%.

[0040] Wherein, the particle size Dv of the natural graphite 10 The preferred size is 2μm-10μm.

[0041] Wherein, the particle size Dv of the natural graphite 90 The optimal range is 30μm-50μm.

[0042] Wherein, the particle size Dv of the natural graphite 50 The optimal range is 10μm-30μm.

[0043] In some embodiments, the degree of graphitization of the natural graphite is 92%, 94%, 96%, 98%, or 99%.

[0044] In some embodiments, the Dv of the natural graphite 10 It is 10μm or 15μm.

[0045] In some embodiments, the Dv of the natural graphite 50 The sizes are 10μm, 15μm, 20μm, 30μm, or 35μm.

[0046] In some embodiments, the natural graphite satisfies: a graphitization degree of 96%, a Dv 90 of 50 μm or 55 μm.

[0047] In some embodiments, the natural graphite satisfies: a graphitization degree of 96%, a Dv 10 of 10 μm, a Dv 50 of 15 μm, a Dv 90 of 55 μm.

[0048] In some embodiments, the natural graphite satisfies: a graphitization degree of 96%, a Dv 10 of 15 μm, a Dv 50 of 20 μm, a Dv 90 of 50 μm.

[0049] In some embodiments, the natural graphite satisfies: a graphitization degree of 96%, a Dv 10 of 10 μm, a Dv 50 of 20 μm, a Dv 90 of 50 μm.

[0050] In some embodiments, the natural graphite satisfies: a graphitization degree of 96%, a Dv 10 of 10 μm, a Dv 50 of 30 μm, a Dv 90 of 50 μm.

[0051] In some embodiments, the natural graphite satisfies: a graphitization degree of 96%, a Dv 10 of 10 μm, a Dv 50 of 35 μm, a Dv 90 of 50 μm.

[0052] In some embodiments, the natural graphite satisfies: a graphitization degree of 92%, a Dv 10 of 10 μm, a Dv 50 of 20 μm, a Dv 90 of 50 μm.

[0053] In some embodiments, the natural graphite satisfies: a graphitization degree of 94%, a Dv 10 of 10 μm, a Dv 50 of 20 μm, a Dv 90 of 50 μm.

[0054] In some embodiments, the natural graphite satisfies: a graphitization degree of 98%, a Dv 10 of 10 μm, a Dv 50 of 20 μm, a Dv 90 of 50 μm.

[0055] In some embodiments, the natural graphite satisfies: a graphitization degree of 99%, a Dv 10 10 μm, a Dv 50 20 μm, a Dv 90 50 μm.

[0056] In the present application, the electrolyte further comprises a lithium salt, and the lithium salt comprises one or more of lithium hexafluorophosphate, lithium bisfluorosulfonylimide, lithium bis(trifluoromethyl)sulfonylimide, lithium acetate, lithium methylsulfonate and lithium trifluoromethylsulfonate.

[0057] Preferably, the content of the lithium salt is 12 wt% to 16 wt%, and the percentage is the percentage of the mass of the lithium salt in the mass of the electrolyte.

[0058] In some embodiments, the lithium salt is LiPF6, and the content of the LiPF6 is 12 wt%.

[0059] The present application is further illustrated by the following examples, but the present application is not limited to the scope of the examples. In the following examples, the experimental methods not specified in the examples are selected according to the conventional methods and conditions, or according to the instructions of the commercial products.

[0060] The structures of the compounds involved in the examples and comparative examples are shown in the following table:

[0061]

[0062] The above compounds are commercially available or synthesized by the conventional methods in the art.

[0063] Preparation method of lithium ion batteries in Examples 1-25 and Comparative Examples 1-2

[0064] (1) Preparation of electrolyte:

[0065] In an argon glove box with a water content of less than 10 ppm, an ether solvent was prepared by mixing the components in the proportions shown in Table 1, and then battery-grade ethylene carbonate (EC) was mixed with the ether solvent in a certain mass ratio to form an organic solvent. A certain amount of vinylene carbonate (VC) and LiPF6 were mixed with the foregoing organic solvent to obtain an electrolyte. In the obtained electrolyte, the content of LiPF6 was 12%, and the content of each component was a weight percentage calculated based on the total weight of the electrolyte.

[0066] (2) Preparation of positive electrode sheet

[0067] LiFePO4 as the positive active material, polyvinylidene fluoride as the binder and Super P as the conductive agent, mixed in a weight ratio of 97:1:2, added with N-methyl pyrrolidone (NMP), stirred under the action of a vacuum stirrer until the system became uniform and transparent, to obtain a positive slurry; the positive slurry was uniformly coated on an aluminum foil; the aluminum foil was transferred to an oven for drying after being air-dried at room temperature, and then cold-pressed, cut to obtain a positive electrode sheet.

[0068] (3) Preparation of the negative electrode sheet

[0069] The natural graphite (graphitization degree of the natural graphite is 96%, Dv10 is 10 μm, Dv50 is 20 μm, and Dv90 is 50 μm) was used as the negative active material, Super P was used as the conductive agent, carboxymethyl cellulose sodium (CMC-Na) was used as the thickening agent, and butadiene-styrene rubber (SBR) was used as the binder, mixed in a mass ratio of 96:1:1:2, added with deionized water, and obtained under the action of a vacuum stirrer to obtain a negative slurry; the negative slurry was uniformly coated on a negative current collector copper foil; the copper foil was transferred to an oven for drying after being air-dried at room temperature, and then cold-pressed, cut to obtain a negative electrode sheet.

[0070] (4) Preparation of the separator:

[0071] A polypropylene film was used as the separator.

[0072] (5) Preparation of the lithium ion battery:

[0073] The above positive electrode sheet, separator and negative electrode sheet were laminated in sequence, with the separator between the positive and negative electrodes to play a separating role. Then, an aluminum plastic film was wrapped outside, transferred to a vacuum oven for drying at 120°C, injected with 3.0 g / Ah of the above prepared electrolyte, sealed, electrolyzed and finally prepared into a lithium ion battery with a capacity of 1 Ah.

[0074] Table 1 Composition of the electrolyte

[0075]

[0076] Preparation method of the lithium ion battery in Examples 26-44

[0077] (1) Preparation of the electrolyte:

[0078] In an argon atmosphere glove box with water content <10 ppm, the ether solvent was prepared by mixing the fluorinated ether solvent and DME in Table 2 according to a mass ratio of 1:1, and then mixing the battery grade ethylene carbonate (EC) with the ether solvent according to a mass ratio of 2:8 to form an organic solvent. A certain amount of VC and LiPF6 were mixed with the above organic solvent to obtain an electrolyte; the content of VC in the obtained electrolyte was 2.5%, the content of LiPF6 was 12%, and the content was the weight percentage calculated based on the total weight of the electrolyte;

[0079] (2) Preparation of the positive electrode sheet

[0080] LiFePO4 was used as the positive electrode active material, polyvinylidene fluoride was used as the binder, and Super P was used as the conductive agent, and they were mixed according to a weight ratio of 97:1:2, N-methyl pyrrolidone (NMP) was added, and stirring was performed under the action of a vacuum stirrer until the system became uniform and transparent to obtain a positive electrode slurry; the positive electrode slurry was uniformly coated on an aluminum foil; the aluminum foil was dried in an oven after being dried at room temperature, and then cold-pressed and cut to obtain a positive electrode sheet.

[0081] (3) Preparation of the negative electrode sheet

[0082] The graphite in Table 2 was used as the negative electrode active material, Super P was used as the conductive agent, sodium carboxymethyl cellulose (CMC-Na) was used as the thickening agent, and styrene butadiene rubber (SBR) was used as the binder, and they were mixed according to a mass ratio of 96:1:1:2, deionized water was added, and a negative electrode slurry was obtained under the action of a vacuum stirrer; the negative electrode slurry was uniformly coated on a negative electrode current collector copper foil; the copper foil was dried at room temperature, and then transferred to an oven for drying, and then cold-pressed and cut to obtain a negative electrode sheet.

[0083] (4) Preparation of the separator:

[0084] A polypropylene film was used as the separator.

[0085] (5) Preparation of the lithium ion battery:

[0086] The above positive electrode sheet, separator, and negative electrode sheet were stacked in sequence, and the separator was placed between the positive electrode and the negative electrode to play a separating role. Then, an aluminum plastic film was wrapped outside, transferred to a vacuum oven for drying at 120°C, and then 3.0 g / Ah of the above prepared electrolyte was injected and sealed, and then electrolytic liquefaction was performed, and finally a lithium ion battery with a capacity of 1 Ah was prepared.

[0087] Table 2

[0088]

[0089] Effect Example 1

[0090] Test of the electrochemical window of the electrolyte:

[0091] The electrolyte prepared according to the above configuration is placed in an electrochemical cell, with Pt as the working electrode, Li metal as the reference electrode and the counter electrode, and positive or negative scanning is started at 10 mV / s from OCV. The oxidation potential value and the reduction potential value are taken as the peak position of the maximum oxidation / reduction peak in the LSV process, and the results are recorded in Tables 3 and 5.

[0092] Effect Example 2

[0093] (1) High-temperature cycle performance test

[0094] In an oven at 45℃, the battery is cycled at 1C current in the range of 2.0V~3.8V, and the discharge capacity of each cycle is recorded. When the battery capacity reaches 80% of the first cycle capacity, the test is ended, and the cycle number is recorded as the high-temperature cycle performance effect data, which is recorded in Tables 3-5.

[0095] (2) Direct current resistance (DCR) test

[0096] At 25℃, when the battery is discharged to 50% SOC (state of charge, reflecting the remaining capacity of the battery) at 1C current, the current is increased to 4C and maintained for 30s. The difference between the updated stable voltage and the original platform voltage is detected, and the ratio of this value to the 3C current value is the direct current resistance of the battery. The initial DCR of the battery is obtained by performing the above DCR test after the first full charge.

[0097] (3) Low-temperature discharge capacity retention rate test

[0098] After the lithium ion battery of the example and the comparative example is fully charged, it is placed in a constant temperature oven at 0℃, and after sufficient cooling, it is discharged at 1C rate to the cut-off voltage. The percentage of its capacity relative to the initial discharge capacity is calculated, which is the low-temperature discharge capacity retention rate.

[0099] The cut-off voltage of charging and discharging is as follows: 2.0V~3.8V.

[0100] Table 3

[0101]

[0102] The lithium ion battery provided by the application has good high-temperature cycle performance and a wide chemical window. In some specific embodiments, the electrochemical window can be -0.46V~4.88V or wider, the discharge capacity retention rate at 0℃ is above 64%, and the 45℃ cycle to 80% SOC can reach 745 cycles or more.

[0103] The electrolyte of Comparative Example 1 does not contain a fluorinated ether solvent, and its electrochemical window is only -0.25V~4.02V, the discharge capacity retention rate at 0℃ is 33%, and the cycle life at 45℃ is 566 cycles when the SOC is 80%, which is significantly lower than that of the electrolyte of the present application.

[0104] Although the electrolyte of Comparative Example 2 also contains a fluorinated ether solvent, the structure of the fluorinated ether solvent is different from that of the fluorinated ether solvent of the present application. Although the low-temperature discharge capacity retention rate of the electrolyte of Comparative Example 2 is comparable to that of the electrolyte of the present application, the high-temperature cycle performance of the electrolyte of Comparative Example 2 is significantly different from that of the electrolyte of the present application.

[0105] Examples 1-10 verify the effects of different types and contents of fluorinated ether solvents on the oxidation potential, reduction potential, low-temperature discharge capacity retention rate, and high-temperature cycle performance. As can be seen from the effect data in Table 3, the electrochemical window of the electrolyte of Examples 1-10 is wide, and in the preferred examples, it reaches a wide window of -0.87V~5.50V. At the same time, the electrolyte also has good high-temperature and low-temperature performance. It can also be seen that by adding Compound 1 or Compound 2 in an appropriate proportion, the low-temperature discharge rate and high-temperature cycle stability of the battery are significantly improved. However, when the content of the fluorinated ether solvent is too high, the high-temperature cycle performance of the battery is affected.

[0106] Examples 11-17 verify the effects of different proportions of VC on the high-temperature cycle performance and initial DCR of lithium ion batteries. As can be seen from the data in Table 4, by adding an appropriate amount of VC in the electrolyte, the high-temperature cycle performance of the battery is improved while maintaining a reasonable impedance level.

[0107] Examples 18-24 verify the effects of different amounts of DTD on the high-temperature cycle performance and initial DCR of lithium ion batteries with the same amount of VC. It can be seen that the content of DTD within a certain range, in combination with VC, can improve the high-temperature cycle performance of the battery and reduce the direct current resistance.

[0108] Example 25 differs from Example 1 in that the formulation of the organic solvent is different. It can be seen that different proportions of ether solvents can also achieve good high-temperature cycle performance. In addition, the low-temperature capacity retention rate of Example 25 is also measured to be 86%, which shows that different proportions of ether solvents can also achieve good low-temperature performance.

[0109] Table 4

[0110]

[0111] Examples 26-44 verify the high temperature cycle performance of lithium ion batteries with two groups of electrolyte compositions being the same and negative active materials being different, wherein, Examples 26-34 and 44 are natural graphite materials or artificial graphite with different graphitization degrees or particle sizes as negative active materials when compound 1 is used as fluoroether compound in electrolyte; Examples 35-43 are natural graphite materials with different graphitization degrees or particle sizes as negative active materials when compound 2 is used as fluoroether compound in electrolyte; it can be seen that the selection of natural graphite with different graphitization degrees or particle sizes as negative active material has certain influence on the high temperature cycle performance of lithium ion batteries. In addition, the low temperature discharge capacity retention rate of Example 44 is measured to be 45%, which may be caused by the structural defects of artificial graphite itself.

[0112] Table 5

[0113]

[0114] The above described examples are only part of the embodiments of the present application, which facilitate the understanding and use of the present application by those skilled in the art. Obviously, any skilled person in the art can make slight modifications or changes to the present embodiments without creative labor and apply them to other embodiments. Therefore, the present application is not limited to the above described examples, and any equivalent changes, simple modifications and modifications within the scope of the present application still belong to the scope of the present application.

Claims

1. A lithium-ion battery, characterized by, It comprises a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte; wherein the positive electrode sheet comprises a positive electrode active material, the positive electrode active material is lithium iron phosphate; The negative electrode sheet comprises a negative electrode active material, the negative electrode active material is natural graphite, and the natural graphite satisfies the following conditions (a)-(d): (a) The graphitization degree of the natural graphite is 94%-98%; (b) the particle size Dv 10 is 2 μm - 10 μm; (c) the particle size Dv 90 is 30 pm - 50 pm; and, (d) the particle size Dv 50 is 10 μm - 30 μm; The electrolyte comprises an ether solvent, the ether solvent comprises a fluorinated ether solvent and a non-fluorinated ether solvent; the fluorinated ether solvent is a compound represented by the following formula I: Formula I, Wherein, R2 is C4 alkylene or C4 fluorinated alkylene, and the number of fluorine atoms in R2 is m, m≥0; R1 and R3 are each independently methyl or fluorinated methyl, and the total number of fluorine atoms in R1 and R3 is n, n≥1; and m+n=4; The content of the ether solvent is greater than 60wt%, the percentage is the mass percentage of the ether solvent in the mass of the electrolyte; the content of the fluorinated ether solvent is 10wt%-60wt%, the percentage is the mass percentage of the fluorinated ether solvent in the total mass of the ether solvent; The electrolyte further comprises an additive, the additive comprises vinylene carbonate, and the content of the vinylene carbonate is 1wt%-4wt%, the percentage is the mass percentage of the additive in the mass of the electrolyte.

2. The lithium-ion battery of claim 1, wherein, The compound represented by the formula I is selected from at least one of the following compounds: 、 、 Compound 1 Compound 2 、 、 Compound 3 Compound 4 and , Compound 5 Compound 6.

3. The lithium-ion battery of claim 1, wherein, The non-fluorinated ether solvent is one or more selected from dimethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether.

4. The lithium-ion battery of claim 1, wherein, The additive further comprises one or both of a sulfate and a sulfonate; the sulfate comprises vinyl sulfate; the sulfonate comprises one or both of methyl methylene disulfonate and 1,3-propane sultone.

5. The lithium-ion battery of claim 1, wherein, The lithium ion battery satisfies one or more of the following conditions (a)-(b): (a) The additive further comprises vinyl sulfate and / or methyl methylene disulfonate, and the content of the vinyl sulfate and / or methyl methylene disulfonate is 0.1wt%-0.8wt%, the percentage is the mass percentage of the additive in the mass of the electrolyte; (b) The additive further comprises vinyl sulfate, and the mass ratio of the vinylene carbonate to the vinyl sulfate is 1:(0.16-0.32).

6. The lithium-ion battery of claim 1, wherein, The electrolyte further comprises a lithium salt, the lithium salt comprises one or more of lithium hexafluorophosphate, lithium bisfluorosulfonylimide, lithium bis(trifluoromethyl)sulfonylimide, lithium acetate, lithium methylsulfonate and lithium trifluoromethylsulfonate; and the content of the lithium salt is 12wt%-16wt%, the percentage is the mass percentage of the lithium salt in the mass of the electrolyte.

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