CN110931862B

CN110931862B - Difunctional electrolyte additive and lithium ion battery electrolyte containing same

Info

Publication number: CN110931862B
Application number: CN201911055186.XA
Authority: CN
Inventors: 梁大宇; 庞春光; 沈剑; 赵坤; 丁楚雄
Original assignee: Hefei Guoxuan High Tech Power Energy Co Ltd
Current assignee: Hefei Gotion High Tech Power Energy Co Ltd
Priority date: 2019-10-31
Filing date: 2019-10-31
Publication date: 2022-03-11
Anticipated expiration: 2039-10-31
Also published as: CN110931862A

Abstract

The invention discloses a bifunctional electrolyte additive and a lithium ion battery electrolyte containing the same, wherein the bifunctional electrolyte additive is a phosphate ester or phosphite ester compound substituted by a five-membered or six-membered N-containing heterocyclic group, and the five-membered or six-membered N-containing heterocyclic group is one of furan, thiophene, pyrrole, thiazole, imidazole, pyridine, pyrazine, pyrimidine and pyridazine groups. When the battery electrolyte containing the electrolyte additive is used, on one hand, a five-membered or six-membered N-containing heterocyclic group is introduced into an SEI film, so that the ion mobility is improved, and the film forming impedance of the SEI film is reduced; on the other hand, the chemical bonds in the P-O bond and the N-containing heterocyclic group are relatively stable, so that the stability of the formed film is higher under the high-temperature condition, and the high-temperature cycle performance of the lithium ion battery, particularly the high-nickel ternary material battery, is improved. The electrolyte additive prepared by the invention has low cost and convenient use when being applied to battery electrolyte, and has excellent industrial application prospect.

Description

Difunctional electrolyte additive and lithium ion battery electrolyte containing same

Technical Field

The invention belongs to the technical field of lithium ion battery electrolyte, and particularly relates to a bifunctional electrolyte additive and a lithium ion battery electrolyte containing the same.

Background

The lithium ion battery has the remarkable advantages of high energy density, low self-discharge rate, wide use temperature range, long cycle life, no memory effect and the like, and is widely applied to the fields of 3C digital products, new energy automobiles, energy storage power stations, aerospace and the like.

The electrolyte is an essential important component of the lithium ion battery, and has important influence on various performances such as capacity, internal resistance, circulation, multiplying power, safety and the like of the lithium ion battery, but the current commercial electrolyte contains a large amount of carbonate organic solvents, so that the high ionic conductivity and electrochemical stability required by the normal work of the lithium ion battery can be guaranteed, the side reaction of the electrolyte and the surface of an electrode material is intensified under the high-temperature condition, active lithium ions are continuously consumed, more and thicker SEI films are formed, and the lithium ion battery has poor circulation life and obvious impedance increase in the circulation process when being used under the high-temperature condition.

In order to solve the application problem of the lithium ion battery under the high temperature condition, the prior protection method adopts a plurality of measures including surface coating modification of positive and negative electrode materials, application of various cooling devices in a battery module system to reduce the actual working temperature of a battery core, use of electrolyte composition with higher thermal stability, addition of a high-temperature improving additive in the electrolyte and the like, wherein the high-temperature performance improving additive is considered to be an important method which is more convenient, easier, more practical and more effective. The phosphate and phosphite compounds are widely reported high-temperature improvement electrolyte additives, for example, patent CN 109546218A reports a silicon-carbon lithium ion battery electrolyte and a silicon-carbon lithium ion battery using the electrolyte, through the synergistic effect of the combination of the phosphate/phosphite compounds, FEC and DTD, the formed SEI film is compact, has high toughness and is not easy to break, and can be correspondingly changed along with the volume change of a silicon-carbon cathode, thereby improving the cycle performance of the battery, meanwhile, the lithium difluorophosphate and the phosphate/phosphite compounds are matched for use, a passivation film with lower impedance can be formed, the side reaction of the electrolyte and the surface of an electrode material is slowed down, the impedance is reduced along with the increase of the cycle number, and the cycle life of the battery is obviously prolonged. The invention patent CN108470938A discloses a lithium ion battery and an electrolyte thereof, and researches show that cyclic phosphazene compound, fluoro lithium phosphate compound, silane phosphate ester compound, silane phosphite ester compound and at least one of silane borate ester compound in the electrolyte additive can effectively improve the cycle capacity retention rate and storage capacity retention rate of the lithium ion battery containing a high-nickel anode material and have lower direct current internal resistance at low temperature through combination and synergistic action, and can obviously improve the thermal stability of the lithium ion battery.

As can be seen from the above, the reported phosphate/phosphite compounds have better high-temperature cycle improvement effect, but generally have higher film formation impedance, resulting in poorer low-temperature performance, so the methods reported in the above two patents must be adopted to be combined with other additives such as lithium fluorophosphate and the like, and the impedance is reduced through synergistic action, so that on one hand, the method increases the types and cost of electrolyte additives, on the other hand, the combined use of a plurality of additives requires a great deal of optimization work, and the formulation development process is time-consuming and labor-consuming. Therefore, the patent provides a novel pentabasic or hexabasic N-containing heterocyclic group substituted phosphate ester or phosphite ester compound electrolyte additive, which can give consideration to the requirements of high-temperature cycle performance and low impedance performance and has important significance for solving the difficult problems in the field.

Disclosure of Invention

In order to overcome the defects in the prior art, the invention aims to provide a bifunctional electrolyte additive and a lithium ion battery electrolyte containing the same.

In order to achieve the purpose, the invention adopts the technical scheme that:

a bifunctional electrolyte additive is a pentabasic or hexahydric phosphate or phosphite compound substituted by a heterocyclic group containing N, and the structural formula is shown as the formula (I) or the formula (II):

wherein: r₁～R₃Each independently selected from an alkane or alkene having 1 to 26 carbon atoms, a halogen-substituted alkane or alkene having 1 to 26 carbon atoms, and R₁～R₃At least one of them is a five-membered or six-membered N-containing heterocyclic group.

As a preferable technical scheme, the five-membered or six-membered N-containing heterocyclic group is one of furan, thiophene, pyrrole, thiazole, imidazole, pyridine, pyrazine, pyrimidine and pyridazine groups.

As a preferred technical scheme, the five-membered or six-membered N-containing heterocyclic group substituted phosphate or phosphite ester compound is one of three pyrrole phosphate, bis (trifluoromethyl) pyrazine phosphate, three pyrimidine phosphite and bis (vinyl) pyrazine phosphite: the structural formulas are respectively shown in the following formulas (III) to (VI):

the invention also aims to provide a synthesis method of the electrolyte additive, which comprises the following steps: phosphorus oxychloride or phosphorous oxychloride precursor and a five-membered or six-membered N-containing heterocyclic compound are mixed according to a molar ratio of 1: 1-1: 3, dissolving in a solvent, adding a catalyst, and reacting at the temperature of 10-60 ℃ for 3-9h under an inert atmosphere to obtain a final product. Preferably, the phosphoryl chloride or phosphorous oxychloride precursor is one of phosphoric acid triacyl chloride, bis-trifluoromethyl phosphoric acid acyl chloride, phosphorous acid triacyl chloride and bis-vinyl phosphorous acid acyl chloride; the solvent is one of acetone, tetrahydrofuran and N-methyl pyrrolidone; the catalyst is organic base or inorganic base, and further preferably is triethylamine, NaOH or KOH.

The third purpose of the invention is to provide a lithium ion battery electrolyte containing the electrolyte additive, and the lithium ion battery electrolyte further comprises an organic solvent, a lithium salt and a film-forming additive. Preferably, the organic solvent: lithium salt: film forming additive: the electrolyte additive comprises (70-85) by mass: (10-20): (0.5-5): (0.1-2).

In a further embodiment, the organic solvent is at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methylethyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, dimethyl ether, diethyl ether, adiponitrile, succinonitrile, glutaronitrile, dimethyl sulfoxide, sulfolane, 1, 4-butyrolactone, methyl formate, ethyl acetate, methyl propionate, ethyl propionate, butyl propionate and ethyl butyrate; the lithium salt is at least one of lithium hexafluorophosphate, lithium perchlorate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium tetrafluorooxalate phosphate, lithium bis (oxalate) borate, lithium difluoro (oxalate) borate, lithium bis (trifluoromethane) sulfonyl imide and lithium bis (fluorosulfonyl) imide.

In a further aspect, the film-forming additive is selected from one of the following compounds: substituted or unsubstituted vinylene carbonate and its derivatives, the substituents being selected from halogen, amino, cyano, nitro, carboxyl or sulfonic acid groups; vinyl ethylene carbonate and derivatives thereof, sultone and derivatives thereof, sulfimide and derivatives thereof, nitriles and derivatives thereof, sulfones and derivatives thereof, amides and derivatives thereof, or acid anhydride and derivatives thereof.

The fourth purpose of the invention is to provide a lithium ion battery containing the lithium ion battery electrolyte. The battery also comprises a shell and a battery cell sealed in the shell, wherein the battery cell comprises a positive electrode, a negative electrode and a diaphragm positioned between the positive electrode and the negative electrode.

When the additive is applied to the lithium ion battery electrolyte, on one hand, the five-membered or six-membered N-containing heterocyclic group is introduced into an SEI film, so that the ion mobility is improved, and the film forming impedance of the SEI film is reduced; on the other hand, because the P atom in the P-O bond contains a vacant orbit, more chemical bonds can be formed when the P atom is bonded with an oxygen atom containing a lone pair electron, and therefore, the P-O bond is more stable than the C-O bond in the conventional SEI film, so that the film forming stability under the high-temperature condition is higher.

The invention has the following beneficial effects:

1. the electrolyte additive belongs to a bifunctional electrolyte additive, and can simultaneously realize the effects of improving high-temperature cycle performance and reducing film-forming impedance;

2. the electrolyte additive disclosed by the invention is low in cost when applied to the lithium ion battery electrolyte, few in combined additive variety and simpler in formula screening and optimizing process.

Drawings

Fig. 1 is a graph of capacity retention versus cycle life at 45 ℃ cycling for experimental cell 1 and experimental cell 6.

Detailed Description

The present invention will be further described with reference to the following examples. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

Preparing an electrolyte additive represented by formula (III): tri-pyrrole phosphoric acid ester

Adding 500ml of acetone into a 2000ml three-neck flask provided with an electric stirrer, a reflux condenser tube and a thermometer, adding 0.2mol of phosphoric acid triacyl chloride, adding 0.6mol of pyrrole, adding 0.02mol of triethylamine as a catalyst, controlling the reaction temperature to be between 10 ℃, controlling the reaction time to be 9h, continuously introducing argon gas in the reaction process to keep an inert reaction atmosphere, fully stirring to obtain a reaction solution, and obtaining the tripyrrole phosphate after the reaction solution is subjected to filtration separation and chromatographic separation, wherein the structure is shown as a compound formula (III):

the preparation method of the lithium ion battery electrolyte taking the tripyrrole phosphate as the electrolyte additive comprises the following specific steps:

in an argon glove box with the water content controlled to be less than or equal to 10ppm, Ethylene Carbonate (EC) and Ethyl Methyl Carbonate (EMC) are mixed according to the mass ratio of EC to EMC of 3: 7, uniformly mixing to obtain an organic solvent, slowly adding lithium hexafluorophosphate into the organic solvent, adding vinylene carbonate and trispyrrole phosphate after the lithium hexafluorophosphate is completely dissolved, and uniformly stirring to obtain the electrolyte 1, wherein the mass fractions of the lithium hexafluorophosphate, the organic solvent, the vinylene carbonate and the trispyrrole phosphate are respectively 13.5%, 84.5%, 1.5% and 0.5%.

The preparation method of the lithium ion battery comprises the following specific steps:

the method comprises the following steps of mixing a silicon-based negative electrode material (NMC811) serving as a positive electrode active substance, acetylene black serving as a conductive agent and polyvinylidene fluoride serving as a binder according to the following mass ratio NMC 622: acetylene black: and (3) mixing the polytetrafluoroethylene (95: 2.5: 2.5), adding N-methyl pyrrolidone after mixing, fully stirring and uniformly mixing to form uniform anode slurry, uniformly coating the anode slurry on a 15-micron-thick aluminum foil, and drying to obtain the anode sheet.

Manufacturing a laminated battery containing soft packages in a dry environment with the dew point temperature controlled below-40 ℃, stacking the prepared positive plate, the diaphragm and the graphite negative plate in sequence, ensuring that the diaphragm completely separates the positive plate from the negative plate, packaging and welding a tab by using an aluminum plastic film to form the battery to be injected with liquid, baking the moisture content of the battery to be below 300ppm before the liquid injection, injecting an electrolyte 1, and sealing, forming and grading to obtain the experimental battery 1.

Example 2

The additive of formula (III) is prepared as described in example 1, namely the tripyrrole phosphate; then preparing an electrolyte 2, wherein the mass fractions of lithium hexafluorophosphate, an organic solvent, vinylene carbonate and tris-pyrrole phosphate in the electrolyte 2 are respectively 13.5%, 83%, 1.5% and 2% which are different from the electrolyte 1; finally, an experimental cell 2 containing the electrolyte 2 was prepared.

Example 3

Preparing an electrolyte additive represented by formula (IV): bis (trifluoromethyl) pyrazine phosphate

Adding 500ml tetrahydrofuran into a 2000ml three-neck flask provided with an electric stirrer, a reflux condenser pipe and a thermometer, then adding 0.2mol of bis (trifluoromethyl) phosphoryl chloride, adding 0.2mol of pyrazine compound, taking 0.01mol of NaOH as a catalyst, controlling the reaction temperature between 60 ℃, controlling the reaction time to be 3h, continuously introducing argon gas in the reaction process to keep an inert reaction atmosphere, fully stirring to obtain a reaction solution, filtering and separating the reaction solution by chromatography to obtain bis (trifluoromethyl) pyrazine phosphate, wherein the structure is shown as a compound formula (IV)

An electrolyte 3 and an experimental battery 3 were prepared by the method of preparing an electrolyte and a battery according to example 1, using bis-trifluoromethyl pyrazine phosphate represented by formula (IV) as an electrolyte additive; wherein, the mass fractions of lithium hexafluorophosphate, organic solvent, vinylene carbonate and bis-trifluoromethyl pyrazine phosphate in the electrolyte 3 are respectively 13.5%, 84.5%, 1.5% and 0.5%.

Example 4

Preparing an electrolyte additive represented by formula (V): tri-pyrimidine phosphites

Adding 500ml of N-methyl pyrrolidone into a 2000ml three-neck flask provided with an electric stirrer, a reflux condenser tube and a thermometer, then adding 0.2mol of phosphorous acid triacyl chloride, 0.6mol of pyrimidine and 0.01mol of KOH as a catalyst, controlling the reaction temperature to be 30 ℃, controlling the reaction time to be 6h, continuously introducing argon in the reaction process to keep an inert reaction atmosphere, fully stirring to obtain a reaction liquid, and obtaining the tri-pyrimidine phosphite ester after the reaction liquid is subjected to filtration separation and chromatographic separation, wherein the structure is shown as a compound formula (V):

an electrolyte 4 and an experimental battery 4 were prepared by the method of example 1 using a tripyrimidine phosphite of the formula (V) as an electrolyte additive; wherein, the mass fractions of lithium hexafluorophosphate, organic solvent, vinylene carbonate and tris-pyrimidine phosphite in the electrolyte 4 are respectively 13.5%, 84.5%, 1.5% and 0.5%.

Example 5

Preparing an electrolyte additive represented by formula (VI): bis (vinyl pyrazine) phosphites

Adding 500ml of acetone into a 2000ml three-neck flask provided with an electric stirrer, a reflux condenser pipe and a thermometer, then adding 0.2mol of divinyl phosphite acyl chloride, 0.2mol of pyrazine compound and 0.02mol of triethylamine as a catalyst, controlling the reaction temperature to be 60 ℃, controlling the reaction time to be 6h, continuously introducing argon gas in the reaction process to keep an inert reaction atmosphere, fully stirring to obtain a reaction solution, and filtering and separating the reaction solution and performing chromatographic separation to obtain the divinyl pyrazine phosphite ester, wherein the structure is shown in a compound formula (VI):

an electrolyte 5 and an experimental battery 5 were prepared by the method of preparing the electrolyte and the battery in example 1 by using the divinyl pyrazine phosphite represented by the formula (VI) as an electrolyte additive; wherein, the mass fractions of lithium hexafluorophosphate, organic solvent, vinylene carbonate and divinyl pyrazine phosphite ester in the electrolyte 5 are respectively 13.5%, 84%, 1.5% and 0.5%.

Comparative example 1

An electrolyte 6 and an experimental cell 6 were prepared in the same manner as in example 1, except that only vinylene carbonate was added and no electrolyte additive was added after lithium hexafluorophosphate was completely dissolved in the preparation of the electrolyte 6, wherein the mass fractions of lithium hexafluorophosphate, organic solvent and vinylene carbonate were 13.5%, 85% and 1.5%, respectively.

Comparative example 2

An electrolyte 7 and an experimental cell 7 were prepared in the same manner as in example 1, except that vinylene carbonate and tris (trifluoromethyl) phosphate were added after lithium hexafluorophosphate was completely dissolved during the preparation of the electrolyte 7, wherein the mass fractions of lithium hexafluorophosphate, organic solvent, vinylene carbonate and tris (trifluoromethyl) phosphate additive were 13.5%, 84.5%, 1.5% and 0.5%, respectively.

Comparative example 3

An electrolytic solution 8 and an experimental cell 8 were prepared in the same manner as in example 1, except that vinylene carbonate, tris (trifluoromethyl) phosphate and lithium difluorophosphate were added after lithium hexafluorophosphate was completely dissolved during the preparation of the electrolytic solution 8, wherein the mass fractions of lithium hexafluorophosphate, organic solvent, vinylene carbonate, tris (trifluoromethyl) phosphate and lithium difluorophosphate were 13.5%, 83.5%, 1.5%, 0.5% and 1%, respectively.

The compositions and contents of the electrolytes of examples 1 to 5 and comparative examples 1 to 3 are shown in the following table 1:

TABLE 1 compositions and contents of electrolytes prepared in examples 1 to 5 and comparative examples 1 to 3

The experimental batteries 1 to 8 prepared in examples 1 to 5 and comparative examples 1 to 3 were subjected to high temperature cycle performance detection and EIS resistance performance test, respectively, and the specific steps were as follows:

(1) high temperature cycle performance testing

Under the high-temperature test condition of 45 ℃, the experimental batteries 1-8 are respectively subjected to charge-discharge cycle performance test at a charge-discharge rate of 1C, the charge-discharge voltage interval is set to be 3.0-4.2V, the cycle test is carried out for 150 times, and a curve graph of the capacity retention rate-cycle life of the experimental batteries is recorded.

(2) EIS impedance growth rate test after 150 weeks high temperature cycling

Before the high-temperature cycle test, the experimental batteries of examples 1 to 5 and comparative examples 1 to 3 were subjected to capacity grading and then fully charged, fresh battery impedance curves were tested using an EIS impedance tester, and battery interface SEI film impedance R was calculated by an equivalent circuit fitting method₀The test frequency range is 0.01-10kHz, and the disturbance voltage is set to be 10 mV. The interfacial SEI film resistance R of the battery after 150 weeks of cycle is calculated and measured according to the same method₁₅₀Then the impedance growth rate is equal to (R)₁₅₀-R_O)*100％/R_O。

The test results of the experimental cells of examples 1 to 5 and comparative examples 1 to 3 are shown in table 2 below:

table 2 test data for experimental cells

As can be seen from the experimental data in table 2:

(1) the electrolyte additives in the formulas (III) - (VI) are used in the electrolyte of the experimental batteries 1-5, and compared with the battery prepared by a comparative example, the capacity and the first efficiency of the experimental batteries 1-5 are higher, which shows that the electrolyte additives prepared by the invention have smaller influence on the capacity and the first efficiency of the battery; the capacity retention rate is more than 89% after the battery is cycled for 150 weeks, and the SEI film impedance growth rate is less than 13%, which shows that the electrolyte additive prepared by the invention effectively inhibits the SEI film impedance growth in the high-temperature cycle process.

(2) The electrolyte 6 in the experimental cell 6 prepared in comparative example 1 did not use an electrolyte additive and contained only a vinylene carbonate film-forming additive. As can be seen from table 1, the capacity retention rate of the experimental battery 6 was significantly reduced compared to the experimental battery 1 after the battery was cycled for 150 weeks; the electrolyte does not contain the electrolyte additive, the film-forming protection force is insufficient only under the action of the film-forming additive, and the electrolyte is continuously decomposed in the high-temperature circulation process, so that the capacity retention rate is only 86.5 percent after the circulation is carried out for 150 weeks; the impedance growth rate after circulation is also higher, reaching 17.3%.

(3) The test results of the experimental battery 7 prepared in comparative example 2 show that the use of the conventional phosphate additive reduces the first effect and capacity of the battery, and the increase in the resistance of the SEI film during the cycle may be caused by the fact that the viscosity of the phosphate additive is high and the film formation is too thick, and the side effects of the phosphate additive can be improved only when the electrolyte 7 is used in combination with other additives such as lithium difluorophosphate.

In conclusion, compared with a single film forming additive or a traditional phosphate ester combined additive scheme, the electrolyte additive disclosed by the invention has more obvious effects on the aspects of improving high-temperature circulation and inhibiting the increase of SEI (solid electrolyte interphase) film impedance, and has smaller influence on electrochemical properties such as the capacity and the first effect of a lithium ion battery.

The above-mentioned embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solution of the present invention by those skilled in the art should fall within the protection scope defined by the claims of the present invention without departing from the spirit of the present invention.

Claims

1. A bifunctional electrolyte additive, characterized by: is a phosphate or phosphite compound substituted by five-membered or six-membered heterocyclic groups containing N, and the structural formula is shown as formula (I) or formula (II):

formula (I) formula (II)

Wherein: R1-R3 are respectively and independently selected from alkane or alkene with 1-26 carbon atoms and halogen substituted alkane or alkene with 1-26 carbon atoms, and at least one of R1-R3 is a five-membered or six-membered N-containing heterocyclic group;

the five-membered or six-membered N-containing heterocyclic group substituted phosphate ester or phosphite ester compound is one of three pyrrole phosphate ester, bis (trifluoromethyl) pyrazine phosphate ester, three pyrimidine phosphite ester and bis (vinyl) pyrazine phosphite ester.

2. The method of synthesizing an electrolyte additive according to claim 1, wherein: the method comprises the following steps: phosphorus oxychloride or phosphorous oxychloride precursor and a five-membered or six-membered N-containing heterocyclic compound are mixed according to a molar ratio of 1: 1-1: 3, dissolving in a solvent, adding a catalyst, and reacting at the temperature of 10-60 ℃ for 3-9h under an inert atmosphere to obtain a final product.

3. The method of synthesis according to claim 2, characterized in that: the phosphoryl chloride or phosphorous oxychloride precursor is one of phosphoric acid triacyl chloride, bis-trifluoromethyl phosphoric acid acyl chloride, phosphorous acid triacyl chloride and bis-ethylene phosphorous acid acyl chloride; the solvent is one of acetone, tetrahydrofuran and N-methyl pyrrolidone; the catalyst is organic base or inorganic base.

4. A lithium ion battery electrolyte comprising the electrolyte additive of claim 1, wherein: the lithium ion battery electrolyte also comprises an organic solvent, lithium salt and a film forming additive.

5. The lithium ion battery electrolyte of claim 4, wherein: the organic solvent is: lithium salt: film forming additive: the electrolyte additive comprises (70-85) by mass: (10-20): (0.5-5): (0.1-2).

6. The lithium ion battery electrolyte of claim 4, wherein: the organic solvent is at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methylethyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, dimethyl ether, diethyl ether, adiponitrile, succinonitrile, glutaronitrile, dimethyl sulfoxide, sulfolane, 1, 4-butyrolactone, methyl formate, ethyl acetate, methyl propionate, ethyl propionate, butyl propionate and ethyl butyrate; the lithium salt is at least one of lithium hexafluorophosphate, lithium perchlorate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium tetrafluorooxalate phosphate, lithium bis (oxalate) borate, lithium difluoro (oxalate) borate, lithium bis (trifluoromethane) sulfonyl imide and lithium bis (fluorosulfonyl) imide.

7. The lithium ion battery electrolyte of claim 4, wherein: the film forming additive is selected from one of the following compounds: substituted or unsubstituted vinylene carbonate and its derivatives, the substituents being selected from halogen, amino, cyano, nitro, carboxyl or sulfonic acid groups; vinyl ethylene carbonate and derivatives thereof, sultone and derivatives thereof, sulfimide and derivatives thereof, nitriles and derivatives thereof, sulfones and derivatives thereof, amides and derivatives thereof, or acid anhydride and derivatives thereof.

8. A lithium ion battery comprising the lithium ion battery electrolyte of claim 4.