CN105514489A - Electrolyte and lithium ion battery containing electrolyte - Google Patents

Abstract

The invention relates to the field of lithium ion batteries, in particular to an electrolyte and a lithium ion battery comprising the electrolyte. The electrolytic solution of the invention includes lithium salt, organic solvent and additives, and the additives include fluoroethylene carbonate, silazane compound and cyclic sulfuric acid ester. The invention also relates to a lithium ion battery containing the electrolyte. The combination of silazane compound and cyclic sulfate is applied to the non-aqueous electrolyte containing fluoroethylene carbonate, which can use cyclic sulfate and fluoroethylene carbonate to have excellent performance in graphite, silicon or tin-based anodes. The SEI film-forming effect can also prevent the cyclic sulfate from causing damage to the cathode-anode interface, thereby achieving the effect of improving the cycle, rate and safety performance of lithium-ion batteries with graphite, silicon or tin-based anodes.

Description

Electrolyte and lithium ion battery containing the same

technical field

The invention relates to the field of lithium ion batteries, in particular to an electrolyte and a lithium ion battery comprising the electrolyte.

Background technique

The high energy density, long cycle life, wide operating temperature range, and environmental protection of lithium-ion batteries have made them the main energy source for mobile electronic devices. However, the rapid development of mobile electronic devices, especially smartphones (lighter and thinner) in recent years, has also put forward higher demands on the energy density of lithium-ion batteries.

In order to increase the energy density of lithium-ion batteries, two commonly used methods are to increase the operating voltage of the positive electrode material and use the negative electrode material with higher discharge capacity. Among them, Si or Sn and their alloy anode materials have become an important development direction for improving the energy density of lithium-ion batteries because of their theoretical specific capacity (4200mAh/g) much higher than that of graphite. However, compared with the graphite anode system, the interface stability of Si or Sn and its alloy anode system is poor, which affects the cycle capacity retention rate. The main reason may be that the SEI film on the surface of Si or Sn and its alloy anode is prone to damage: SEI film Destruction leads to side reactions of solvents on the anode surface, which accelerates the cycle capacity fading of lithium-ion batteries.

In view of this, it is necessary to provide an electrolyte that can improve the charge-discharge cycle performance of Si or Sn and its alloy anode lithium ion batteries.

Contents of the invention

The primary object of the invention is to provide an electrolyte solution.

A second object of the present invention is to propose a lithium ion battery containing the electrolyte.

In order to accomplish the purpose of the present invention, the technical solution adopted is:

The present invention relates to an electrolytic solution, the electrolytic solution includes lithium salt, organic solvent and additives, the additives include fluoroethylene carbonate, the silazane compound shown in formula I and the ring compound shown in formula II sulphate;

Wherein, in formula I, R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , and R ₇ are each independently selected from hydrogen, C _1-6 alkyl, and n is selected from an integer of 1-5;

In formula II, R ₁₁ and R ₁₂ are each independently selected from hydrogen, C _1-6 alkyl, and C _1-6 alkoxy, and n is selected from an integer of 0-2.

Preferably, in formula I, R ₁ is selected from hydrogen or C _1-3 alkyl, R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ are each independently selected from C _1-3 alkyl, n is selected from 1, 2 or 3;

In formula II, R ₁₁ and R ₁₂ are each independently selected from hydrogen or C _1-3 alkyl, and n is selected from 0 or 1.

Preferably, the silazane compound is at least one selected from hexamethyldisilazane, heptamethyldisilazane, hexaethyldisilazane or hexapropyldisilazane.

Preferably, the cyclic sulfate is at least one selected from vinyl sulfate, propylene sulfate, and 4-methyl vinyl sulfate.

Preferably, the mass percent content of the cyclic sulfuric acid ester in the electrolyte is 0.1%-5%.

Preferably, the mass percent content of the silazane compound in the electrolyte is 0.1%-5%.

Preferably, the organic solvent is selected from ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethylene propylene carbonate At least one of ester, 1,4-butyrolactone, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate or ethyl butyrate;

The lithium salt is selected from lithium hexafluorophosphate, lithium difluorophosphate, lithium tetrafluoroborate, lithium bistrifluoromethanesulfonylimide, lithium bis(fluorosulfonyl)imide, lithium bisoxalate borate or lithium difluorooxalate borate at least one.

The invention also relates to a lithium ion battery, comprising a positive electrode sheet containing positive electrode active materials, a negative electrode sheet containing negative electrode active materials, a lithium battery diaphragm and the electrolyte of the invention.

Preferably, the negative electrode material is selected from at least one of carbon materials, silicon-based negative electrode materials, tin-based negative electrode materials, alloy negative electrode materials containing silicon, and alloy negative electrode materials containing tin.

Preferably, the negative electrode active material contains at least one of graphite, silicon or tin.

The beneficial effects that the technical solution of the present invention can achieve are:

Cyclic sulfate and fluoroethylene carbonate (FEC) have excellent SEI film-forming effects on graphite, silicon or tin-based anodes, but the stability of cyclic sulfate is poor, and it is easy to react to generate H ⁺ or Lewis acid. FEC and LiPF ₆ The reaction is also easy to generate H ⁺ or Lewis acid, which will damage the SEI and cause accelerated cycle capacity fading. Silazane compounds have the effect of adsorbing H ⁺ or Lewis acid and undergoing ring-opening reaction. The inventor was surprised to find in the research that adding a certain amount of silazane compound to the non-aqueous electrolyte containing FEC and cyclic sulfuric acid ester can reduce the surface tension and viscosity of the electrolyte to a large extent, and improve the electrolyte's effect on the anode electrode. The wettability of the sheet, and the long branched chain of the silazane compound can form a network structure, and have an inductive effect on the cyclic sulfate and fluoroethylene carbonate, so that it can be uniformly dispersed and passed through the mesh on the anode A uniform and dense protective film is formed on the surface. The three can also form a stable and uniform passivation film on the surface of the positive electrode, which significantly improves the cycle, rate and safety performance of lithium-ion batteries under high voltage.

detailed description

According to one aspect of the present application, a non-aqueous electrolyte in a lithium-ion battery is provided, which can improve the charge-discharge cycle capacity retention rate of a lithium-ion battery containing silicon and/or tin in the anode.

The electrolytic solution includes a lithium salt, an organic solvent and additives, and the additives include fluoroethylene carbonate (FEC), a silazane compound shown in formula I and a cyclic sulfuric acid ester shown in formula II.

The silazane compound of the present invention is shown in formula I:

In formula I, R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , and R ₇ are each independently selected from hydrogen, C _1-6 alkyl, and n is selected from 1-5 integers;

Preferably, R ₁ is selected from hydrogen or C _1-6 alkyl, R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ are each independently selected from C _1-3 alkyl, n is selected from 1, 2 or 3.

As an improvement of the electrolyte of the present invention, the structural formula of the silazane compound is shown in formula (Ia):

In formula Ia, R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , and R ₇ are each independently selected from C _1-3 alkyl groups, and n is selected from 1, 2 or 3.

As a kind of improvement of electrolytic solution of the present invention, silazane compound can be selected from:

Cyclic sulfuric acid ester of the present invention is shown in formula II:

In formula II, R ₁₁ and R ₁₂ are each independently selected from hydrogen, C _1-6 alkyl, and C _1-6 alkoxy, and n is selected from an integer of 0-2.

Preferably, R ₁₁ and R ₁₂ are each independently selected from hydrogen or C _1-3 alkyl, and n is selected from 0 or 1.

As a kind of improvement of electrolytic solution of the present invention, the structural formula of cyclic sulfuric acid ester is as shown in formula (IIa):

As a kind of improvement of electrolytic solution of the present invention, the structural formula of cyclic sulfuric acid ester is as shown in formula (IIb):

As a kind of improvement of electrolytic solution of the present invention, cyclic sulfuric acid ester can be selected from:

The preferred upper limit of the number of carbon atoms in the above-mentioned alkyl group is 6, 5, 4, 3, 2, 1 in sequence; for example, when the upper limit of the number of carbon atoms is 6, the range of the number of carbon atoms of the alkyl group is means 1-6; the most preferable number of carbon atoms of the alkyl group is 1-5, and more preferably 1-3. Alkyl can be chain alkyl or cycloalkyl: chain alkyl includes straight-chain alkyl and branched alkyl; cycloalkyl is saturated alkyl containing alicyclic structure, which may or may not contain Substituents.

The aforementioned C _1-6 alkyl groups include but are not limited to: -CH ₃ , -CH ₂ CH ₃ , -(CH ₂ ) ₂ CH ₃ , -CH(CH ₃ ) ₂ , cyclopropyl, -(CH ₂ ) ₃ CH ₃ ,-CH2CH( _CH3 ) ₂ ,-CH( _CH3 ) _CH2CH3 ,-CH2CH _{( CH3} ) ₂ ,-C( _{CH3 )3 , -} ( _{CH2 ) 4CH3} , -CH ₂ CH ₂ CH(CH ₃ ) ₂ , -CH(CH ₃ )CH ₂ CH ₂ CH ₃ , -CH ₂ CH(CH ₃ )CH ₂ CH ₃ , -CH ₂ C(CH ₃ ) ₃ , cyclohexyl .

As an improvement of the electrolyte of the present invention, the mass percentage of cyclic sulfate in the electrolyte is 0.1% to 5%, and preferably 1% to 5%; the mass percentage of silazane compounds in the electrolyte is The content is 0.1% to 5%, and preferably 0.1% to 3%.

As a kind of improvement of electrolytic solution of the present invention, the nonaqueous solvent of nonaqueous organic electrolytic solution is selected from ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC) , at least one of ethyl methyl carbonate (EMC), ethyl propionate (EP), propyl propionate (PP), methyl propionate (MP), and propyl acetate (PA).

As an improvement of the electrolytic solution of the present invention, the mass fraction of fluoroethylene carbonate (FEC) in the electrolytic solution is 1%-30%.

As an improvement of the electrolytic solution of the present invention, the lithium salt used in the non-aqueous organic electrolytic solution is selected from lithium hexafluorophosphate LiPF ₆ , lithium tetrafluoroborate LiBF ₄ , lithium bistrifluoromethanesulfonylimide LiN(CF ₃ SO ₂ ) ₂ ( LiTFSI for short), lithium dioxalate borate LiB(C ₂ O ₄ ) ₂ (LiBOB for short), lithium difluorooxalate borate LiBF ₂ (C ₂ O ₄ ) (LiDFOB for short); preferably, The lithium salt concentration is 0.9M-1.2M.

Another aspect of the application of the present invention provides a lithium ion battery, comprising a positive electrode sheet containing a positive electrode active material, a negative electrode sheet containing a negative electrode active material, a lithium battery separator and the electrolyte of the present invention.

Preferably, the negative electrode material is selected from at least one of carbon materials, silicon-based negative electrode materials, tin-based negative electrode materials, alloy negative electrode materials containing silicon, and alloy negative electrode materials containing tin. Preferably, the negative electrode active material contains at least one of graphite, silicon or tin. The positive electrode active material of the lithium ion battery is at least one selected from lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide .

Specifically, the negative electrode active material is selected from natural graphite, artificial graphite, mesophase microcarbon spheres, hard carbon, soft carbon, silicon, silicon-carbon composites, Li-Sn alloys, Li-Sn-O alloys, Sn, SnO, At least one of SnO ₂ , lithiated TiO ₂ -Li ₄ Ti ₅ O ₁₂ with spinel structure, and Li-Al alloy.

Below in conjunction with embodiment, further elaborate the present application. It should be understood that these examples are only used to illustrate the present application and are not intended to limit the scope of the present application.

Unless otherwise specified, the contents in the examples are all mass percentages. Wherein, the mass percentage of each component in the organic solvent=100%×the mass of each component of the organic solvent/the quality of the organic solvent; the percentage of each component in the additive=100%×the mass of each component of the additive/non-aqueous total mass of electrolyte.

Examples 1-9

Electrolyte preparation: Mix ethylene carbonate (abbreviated as EC) and diethyl carbonate (abbreviated as DEC) at a mass ratio of EC:DEC=30:70, add a certain mass of lithium hexafluorophosphate (LiPF ₆ ) to make it The concentration in the liquid is 1M; the additive is composed of FEC, silazane compound and cyclic sulfate; wherein the silazane compound is hexamethyldisilazane, and the cyclic sulfate is DTD.

The specific addition method of the electrolyte is shown in Table 1, wherein the addition amounts of FEC, hexamethyldisilazane and DTD are the mass percentages of the electrolyte.

Table 1: Electrolyte addition method

Example non-aqueous organic solvent lithium salt FEC Hexamethyldisilazane DTD Example 1 EC:DEC=3:7 1M _LiPF6 10 0.2 1 Example 2 EC:DEC=3:7 1M _LiPF6 10 0.5 1 Example 3 EC:DEC=3:7 1M _LiPF6 10 1 1 Example 4 EC:DEC=3:7 1M _LiPF6 10 2 1 Example 5 EC:DEC=3:7 1M _LiPF6 10 3 1 Example 6 EC:DEC=3:7 1M _LiPF6 10 1 0.2 Example 7 EC:DEC=3:7 1M _LiPF6 10 1 0.5 Example 8 EC:DEC=3:7 1M _LiPF6 10 1 3 Example 9 EC:DEC=3:7 1M _LiPF6 10 1 5

Preparation of positive electrode sheet: Lithium cobaltate, conductive carbon black (SuperP), binder polyvinylidene fluoride (PVDF) are mixed with N-methylpyrrolidone (NMP) at a mass ratio of 97:1.4:1.6 Lithium-ion battery cathode slurry, coated on the aluminum foil of the current collector; after drying at 85°C, cold pressing; then trimming, cutting, and slitting, drying at 85°C for 4 hours under vacuum conditions, and welding The tabs are made into positive pole pieces for lithium-ion batteries.

Preparation of the negative electrode sheet: graphite and SiO ₂ (75:25) as the anode active material were mixed with conductive carbon black (SuperP), thickener sodium carboxymethyl cellulose (abbreviated as CMC), binder polyacrylic acid ( Abbreviated as PAA) according to the mass ratio of 92:1.0:1.0:5 mixed with pure water to make a slurry, coated on the copper foil of the current collector and dried at 85 °C; then trimming, cutting, and slitting Finally, it was dried under vacuum conditions at 120°C for 12 hours, and the tabs were welded to make negative pole pieces of lithium-ion batteries.

Lithium-ion battery preparation: use polyethylene (abbreviated as PE) porous polymer film as a separator; stack the prepared positive electrode sheet, separator, and negative electrode sheet in order, so that the separator is in the middle of the positive and negative electrode sheets, and wind up to obtain a bare battery. Core; put the bare cell in the outer packaging, inject the electrolyte prepared above into the dried battery, package, stand, and form (0.02C constant current charge to 3.4V, and then 0.1C constant current charge to 3.85V), shaping, capacity testing, and complete the preparation of lithium-ion batteries (the thickness of the soft pack battery is 4.2mm, the width is 32mm, and the length is 82mm).

Comparative example 1-8

Lithium-ion batteries were prepared according to the method of the examples, the only difference being the composition of the additives in the electrolyte. The specific addition method of the electrolyte is shown in Table 2, wherein the addition amounts of FEC, hexamethyldisilazane and DTD are the mass percentages of the electrolyte.

Table 2: Electrolyte addition method

Example non-aqueous organic solvent lithium salt FEC Hexamethyldisilazane DTD Comparative example 1 EC:DEC=3:7 1M _LiPF6 10 — — Comparative example 2 EC:DEC=3:7 1M _LiPF6 10 — 1 Comparative example 3 EC:DEC=3:7 1M _LiPF6 10 1 — Comparative example 4 EC:DEC=3:7 1M _LiPF6 — 1 1 Comparative example 5 EC:DEC=3:7 1M _LiPF6 10 1 0.05 Comparative example 6 EC:DEC=3:7 1M _LiPF6 10 1 6 Comparative example 7 EC:DEC=3:7 1M _LiPF6 10 0.05 1 Comparative example 8 EC:DEC=3:7 1M _LiPF6 10 6 1

(1) Lithium-ion battery cycle performance test

The cycle performance of the lithium-ion batteries prepared in Examples 1-9 and Comparative Examples 1-8 were tested respectively, the method is as follows:

At 25°C, after standing for 30 minutes, charge the lithium-ion battery at a rate of 0.5C to 4.4V, then charge at a constant voltage of 4.4V to 0.05C, and let it stand for 5 minutes, then discharge at a rate of 0.5C To 3.0V, this is a charge-discharge cycle process. The discharge capacity this time is the first discharge capacity of the lithium-ion battery, and then 200 charge-discharge cycle processes are performed.

The capacity retention rate (%) of the lithium-ion battery after N cycles = the discharge capacity of the Nth cycle/the first discharge capacity × 100%.

The test results of the battery cycle performance are shown in Table 3.

Table 3: Lithium-ion battery cycle performance

As can be seen from the test results of Examples 1 to 5 and Comparative Examples 7 and 8, the addition of DTD with a mass fraction of 1% in the electrolytic solution containing 10% FEC in the mass fraction, and the addition of a mass fraction of DTD in the electrolytic solution simultaneously 0.2% to 3% of hexamethyldisilazane, the cycle performance of lithium-ion batteries is significantly improved, and the addition of hexamethyldisilazane is preferably 0.5% to 2%; hexamethyldisilazane If the amount of alkane added is too high or too low, the cycle performance of the battery cannot be improved.

As can be seen from the test results of Examples 3, 6-9 and Comparative Examples 5 and 6, adding mass fraction of 1% hexamethyldisilazane to the electrolytic solution containing 10% FEC, while Adding DTD with a mass fraction of 0.2% to 5%, the cycle performance of the lithium-ion battery is significantly improved. When the content of DTD is 0.2%, the anode film formation is insufficient, and the performance of the lithium-ion battery is less improved. When the DTD content is greater than 0.5 %, the lithium-ion battery exhibits the best cycle performance, continue to increase the DTD content to 5%, because the SEI film generated by the high content of DTD is thicker, the impedance increases, and the side reactions brought by DTD increase significantly, the lithium-ion battery If the cycle performance of DTD cannot be further improved, the addition amount of DTD is preferably 0.5% to 3%. If the amount of DTD added is too high or too low, the cycle performance of the battery cannot be improved.

From the test results of Comparative Examples 1-3, it can be seen that after adding 1% DTD to the electrolyte containing 10% FEC by mass fraction, the cycle capacity retention rate of the battery is significantly improved. However, only 1% hexamethyldisilazane was added to the electrolyte, and the cycle performance of the lithium-ion battery was only slightly improved.

From the test results of Comparative Example 4, it can be seen that without adding FEC to the electrolyte, the cycle performance of the lithium-ion battery is poor, because the SEI film generated by FEC is unstable, and the SEI film is destroyed during the cycle, resulting in a decrease in capacity retention.

(2) Battery rate performance test

The batteries obtained in Examples 1-9 and Comparative Examples 1-8 were all subjected to the following tests:

Discharge the battery at a constant current of 0.5C to 3.0V, put it on hold for 5 minutes, then charge it at a constant current of 0.5C to 4.4V, and charge it at a constant voltage until the cut-off current is 0.05C. C, 2C constant current discharge to cut-off voltage 3.0V. Record the discharge capacity at 0.2C, 1C, 1.5C, and 2C as D1, record the discharge capacity at 0.2C as D0, and based on the discharge capacity at 0.2C, use the following formula to calculate the discharge capacity of the battery at different rates Retention rate (testing 15 batteries, taking the average value), the rate performance of the battery is characterized by the discharge capacity retention rate of the battery at different rates. In addition, the discharge capacity retention rates of each battery at different rates are shown in Table 4.

Battery discharge capacity retention rate = [(D1-D0)/D0] × 100%

Table 4: Lithium-ion battery discharge capacity retention rate

(3) Hot box test

The batteries obtained in Examples 1-9 and Comparative Examples 1-8 were all subjected to the following tests:

1) Charge the battery to 4.4V with a constant current of 1.0C, then charge at a constant voltage until the current drops to 0.05C, and then stop charging; 2) Put the battery in a hot box, and heat up from 25°C at a rate of 5°C/min Start to heat up to 150°C, keep the temperature constant after reaching 150°C, then start timing, observe the state of the battery after 1 hour, the standard for passing this test is: the battery has no smoke, no fire, no explosion, and each group has 5 batteries . The results of the hot box tests for the respective batteries are shown in Table 5. Through the above-mentioned hot box test, the safety performance of the battery is characterized.

Table 5: Hot Box Tests for Li-Ion Batteries

Condition after hot box test Example 1 All 5 batteries passed, no smoke, fire or explosion Example 2 All 4 batteries passed, and the other 1 battery caught fire Example 3 All 5 batteries passed, no smoke, fire or explosion Example 4 All 5 batteries passed, no smoke, fire or explosion Example 5 All 5 batteries passed, no smoke, fire or explosion Example 6 All 5 batteries passed, no smoke, fire or explosion

Example 7 All 5 batteries passed, no smoke, fire or explosion Example 8 All 5 batteries passed, no smoke, fire or explosion Example 9 All 5 batteries passed, no smoke, fire or explosion Comparative example 1 All 5 batteries caught fire Comparative example 2 All 5 batteries caught fire Comparative example 3 1 battery passed, and the other 4 batteries all caught fire Comparative example 4 1 battery passed, and the other 4 batteries all caught fire Comparative example 5 2 batteries passed, and the other 3 batteries all caught fire Comparative example 6 2 batteries passed, and the other 3 batteries all caught fire Comparative example 7 2 batteries passed, and the other 3 batteries all caught fire Comparative example 8 2 batteries passed, and the other 3 batteries all caught fire

From the relevant data in the above Table 4 and Table 5, it can be known that compared with the battery prepared in the comparative example, the battery prepared by the embodiment of the present application has the rate performance at 1C, 1.5C, 2C, and the rate performance at 150 The thermal stability at ℃ has been greatly improved.

Examples 10-18

Lithium-ion batteries were prepared according to the methods of the preceding examples, the only difference being the composition of the electrolyte. The specific addition method of the electrolyte is shown in Table 6, wherein the addition amounts of FEC, hexamethyldisilazane and DTD are the mass percentages of the electrolyte.

Table 6:

The properties of the lithium ion batteries prepared by using the electrolyte formulations of Examples 10-18 are similar to those of the previous examples.

Although the present application is disclosed as above with preferred embodiments, it is not used to limit the claims. Any person skilled in the art can make some possible changes and modifications without departing from the concept of the present application. Therefore, the present application The scope of protection shall be based on the scope defined by the claims of the present application.

Claims (10)

1. an electrolyte, is characterized in that, described electrolyte comprises lithium salts, organic solvent and additive, comprises fluorinated ethylene carbonate, such as formula the silicon nitrogen silane compound shown in I with such as formula the cyclic sulfates shown in II in described additive;

Wherein, in formula I, R ₁, R ₂, R ₃, R ₄, R ₅, R ₆, R ₇independently be selected from hydrogen, C separately _{1 ~ 6}alkyl, n is selected from the integer of 1 ~ 5;

In formula II, R ₁₁, R ₁₂independently be selected from hydrogen, C separately _{1 ~ 6}alkyl, C _{1 ~ 6}alkoxyl, n is selected from the integer of 0 ~ 2.

2. electrolyte according to claim 1, is characterized in that, in formula I, and R ₁be selected from hydrogen or C _{1 ~ 3}alkyl, R ₂, R ₃, R ₄, R ₅, R ₆, R ₇independently be selected from C separately _{1 ~ 3}alkyl, n is selected from 1,2 or 3;

In formula II, R ₁₁, R ₁₂independently be selected from hydrogen or C separately _{1 ~ 3}alkyl, n is selected from 0 or 1.

3. electrolyte according to claim 2, is characterized in that, described silicon nitrogen silane compound is selected from least one in hexamethyldisiloxane, heptamethyldisilazane, hexaethyl disilazine or six propyl group disilazanes.

4. according to electrolyte according to claim 2, it is characterized in that, described cyclic sulfates is selected from least one in sulfuric acid vinyl ester, sulfuric acid propylene, 4-methylsulfuric acid vinyl acetate.

5. electrolyte according to claim 1, is characterized in that, described cyclic sulfates mass percentage is in the electrolytic solution 0.1% ~ 5%.

6. electrolyte according to claim 1, is characterized in that, described silicon nitrogen silane compound mass percentage is in the electrolytic solution 0.1% ~ 5%.

7. electrolyte according to claim 1, is characterized in that,

Described organic solvent is selected from least one in ethylene carbonate, propene carbonate, butylene, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonic acid ester, GBL, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate or ethyl butyrate;

Described lithium salts is selected from least one in lithium hexafluoro phosphate, difluorophosphate, LiBF4, two trifluoromethanesulfonimide lithium, two (fluorine sulphonyl) imine lithium, di-oxalate lithium borate or difluorine oxalic acid boracic acid lithium.

8. a lithium ion battery, is characterized in that, comprises the positive plate containing positive electrode active materials, the electrolyte according to any one of negative plate, lithium battery diaphragm and claim 1 ~ 7 containing negative active core-shell material.

9. lithium ion battery according to claim 8, is characterized in that, described negative material be selected from carbon materials, silicon based anode material, tin base cathode material, alloy material of cathode containing silicon, containing at least one in the alloy material of cathode of tin.

10. lithium ion battery according to claim 9, is characterized in that, containing at least one in graphite, element silicon or tin element in described negative active core-shell material.