CN106340672A - Lithium ion battery non-aqueous electrolyte and lithium ion battery - Google Patents

Abstract

The invention discloses a lithium ion battery non-aqueous electrolyte and a lithium ion battery. The lithium ion battery non-aqueous electrolyte comprises an unsaturated phosphate ester compound and a sulfone compound, and the sulfone compound comprises a cyclic sulfone compound and/or a linear sulfone compound; the unsaturated phosphate ester compound has a structure represented by formula 1; and the cyclic sulfone compound has a structure represented by formula 2, and the linear sulfone compound has a structure represented by formula 3. The non-aqueous electrolyte is characterized in that the unsaturated phosphate ester compound and the sulfone compound are simultaneously added to the electrolyte in order to form a protection film with the advantages of uniform components, moderate thickness and good compactness on an electrode interface; the unsaturated phosphate ester compound cooperates with the sulfone compound to make the electrolyte have good stability on a positive electrode in order to make the battery have excellent high-temperature performances and excellent cycle performances, and the unsaturated phosphate ester compound and the sulfone compound are combined to make the battery have low impedance in order to make the battery have excellent low-temperature performances. The electrolyte lays a foundation for the production of high-quality power batteries.

Description

A kind of lithium-ion battery non-aqueous electrolyte and lithium-ion battery

technical field

The present application relates to the field of lithium-ion battery electrolyte, in particular to a lithium-ion battery non-aqueous electrolyte and a lithium-ion battery.

Background technique

Compared with other batteries, lithium-ion batteries have the advantages of light weight, small size, high working voltage, high energy density, high output power, high charging efficiency, no memory effect and long cycle life. For 3C consumer electronics market. And with the development of new energy vehicles, non-aqueous electrolyte lithium-ion batteries are becoming more and more popular as the power supply system of vehicles. With the continuous improvement of the mileage requirements of new energy vehicles, there is an increasing demand for high energy density of power lithium-ion batteries. The ternary nickel-cobalt-manganese cathode material has become a research hotspot of cathode materials for new energy power batteries due to its high energy density, low cost, excellent performance, and relatively good safety. Improvement, the ternary nickel-cobalt-manganese material power battery is developing in the direction of high voltage.

However, the ternary nickel-cobalt-manganese material has the disadvantage of insufficient high-temperature performance as the positive electrode material. In the ternary nickel-cobalt-manganese material, the nickel element has a strong catalytic effect on the electrolyte, which will catalyze the decomposition of the electrolyte, thereby reducing the discharge capacity. And the accumulation of decomposition products will lead to a significant increase in internal resistance; this situation will become particularly serious under the conditions of high voltage, high temperature and high nickel content, which will greatly deteriorate battery performance and hinder high-voltage ternary nickel-cobalt-manganese The practical application of material batteries in the field of power batteries.

The electrolyte is a key factor affecting the overall performance of the battery. In particular, the additives in the electrolyte are particularly important for the various performances of the battery. Therefore, to give full play to the performance of the power battery of the ternary nickel-cobalt-manganese material, the matching of the electrolyte is the key. The current practical lithium-ion battery electrolyte is a non-aqueous electrolyte with traditional film-forming additives such as vinylene carbonate (abbreviated as VC) or fluoroethylene carbonate (abbreviated as FEC). The addition of VC and FEC ensures excellent battery performance. cycle performance. However, the high voltage stability of VC is poor, and FEC is easy to decompose and produce gas at high temperature. Therefore, under the condition of high voltage and high temperature, it is difficult for these additives to meet the performance requirements of high temperature cycle.

Patent application 201410534841.0 discloses a new film-forming additive of phosphate compound containing triple bonds, which can not only improve high-temperature cycle performance, but also significantly improve storage performance. Sulfone compounds were also reported in the literature very early (Journal of Power Sources 179(2008) 770–779), mainly to improve the stability of high-voltage batteries and improve cycle performance. However, scientific and technical workers in this field have found in their research that the passivation film formed by the three-bond phosphate additive at the electrode interface has poor conductivity, resulting in a large interface impedance, which significantly deteriorates the low-temperature performance, and is particularly easy to cause the battery to operate at low temperature. Under-charging and lithium analysis inhibit the application of non-aqueous lithium-ion batteries under low temperature conditions.

Contents of the invention

The purpose of this application is to provide a new lithium ion battery non-aqueous electrolyte and lithium ion battery.

In order to achieve the above object, the application adopts the following technical solutions:

One aspect of the present application discloses a non-aqueous electrolyte solution for lithium-ion batteries, including unsaturated phosphoric acid esters and sulfone compounds, where the sulfone compounds include cyclic sulfone compounds and/or linear sulfone compounds;

The unsaturated phosphate compound has a structure shown in formula one,

Wherein, R ₁ , R ₂ , and R ₃ are independently selected from hydrocarbon groups with 1-4 carbon atoms, and at least one of R ₁ , R ₂ , and R ₃ is an unsaturated hydrocarbon group containing a double bond or a triple bond;

The cyclic sulfone compound has the structure shown in formula 2, and the linear sulfone compound has the structure shown in formula 3,

Among them, R ₄ , R ₅ , R ₆ , and R ₇ are independently selected from hydrogen atoms, halogens, or alkyl groups with 1-5 carbon atoms, and A is substituted or unsubstituted with 2-6 carbon atoms. An alkylene group, the functional group substituted by it can be a halogen or an alkyl group with 1-3 carbon atoms.

It should be noted that the key point of this application is that the above-mentioned unsaturated phosphoric acid ester compound and sulfone compound are added to the non-aqueous electrolyte of the lithium ion battery at the same time, which overcomes the interface impedance caused by adding the unsaturated phosphoric acid ester compound alone. Defects such as large and low temperature charging and precipitation of lithium. Wherein, the sulfone compound may be a cyclic sulfone compound or a straight chain sulfone compound, or both may be used in combination.

It should also be noted that the application of sulfone compounds in the electrolyte is not the first proposal of this application. After a lot of research and experiments, this application has found that the use of sulfone compounds and the above-mentioned unsaturated phosphate compounds can obtain better performance. High and low temperature performance and cycle performance, thus presenting this application. It can be understood that this application is filed on the basis of patent application 201410534841 and priority is given to patent application 201510397735.7. Therefore, the relevant technical content and terms in the above two patent applications are applicable to this application. In addition, the key point of this application is to use the sulfone compound and the above-mentioned unsaturated phosphate compound in combination. As for the specific sulfone compound and the above-mentioned unsaturated phosphate compound, existing laboratory commonly used or uncommonly used compounds can be used. But, in order to guarantee the performance of non-aqueous electrolytic solution, in the preferred scheme of the present application, the concrete type of sulfone compound and above-mentioned unsaturated phosphoric acid ester compound, even specific compound has been explained and limited, and this will be in the back technology detailed in the plan.

Preferably, the unsaturated phosphate compound of the present application is selected from at least one of the compounds of the structural formula shown in Table 1, that is, the unsaturated phosphate compound is selected from at least one of compounds 1 to 6.

Table 1 Unsaturated phosphoric acid ester compounds used in non-aqueous electrolytes for lithium-ion batteries

It can be understood that whether it is the unsaturated phosphoric acid ester compound shown in formula 1 or the unsaturated phosphoric acid ester compound of compound 1 to compound 6, it is the preferred technical solution of this application, and other unsaturated phosphoric acid ester compounds with similar physical and chemical properties are not excluded. Saturated phosphate compounds.

More preferably, the cyclic sulfone compound is at least one of the structural compounds shown in formula 4 and/or formula 5,

Wherein, R ₈ -R ₁₆ are each independently selected from a hydrogen atom, a halogen or an alkyl group with 1-5 carbon atoms.

More preferably, the sulfone compound is selected from sulfolane, 3-methylsulfolane, 3,3,4,4-tetrafluorosulfolane, sulfolane, dimethylsulfone, methylethylsulfone and diethylsulfone at least one.

It can be understood that no matter the sulfone compounds shown in formulas 2 to 5, or several specifically defined sulfone compounds, are the preferred technical solutions of this application, and other sulfone compounds with similar physical and chemical properties are not excluded.

Preferably, in the non-aqueous electrolyte solution for lithium-ion batteries of the present application, the unsaturated phosphate compound accounts for 0.1%-2% of the total weight of the non-aqueous electrolyte solution for lithium-ion batteries.

Preferably, in the non-aqueous electrolyte solution for lithium-ion batteries of the present application, the unsaturated phosphate compound accounts for 0.2%-1% of the total weight of the non-aqueous electrolyte solution for lithium-ion batteries.

Preferably, in the nonaqueous electrolyte solution for lithium ion batteries of the present application, the sulfone compound accounts for 0.1% to 30% of the total weight of the nonaqueous electrolyte solution for lithium ion batteries.

Preferably, the sulfone compound accounts for 0.1%-10% of the total weight of the non-aqueous electrolyte of the lithium ion battery.

Further preferably, the sulfone compound accounts for 0.5-10% of the total weight of the non-aqueous electrolyte of the lithium-ion battery.

More preferably, the sulfone compound accounts for 1-10% of the total weight of the non-aqueous electrolyte of the lithium-ion battery.

In the lithium-ion battery non-aqueous electrolyte of the present application, when the amount of unsaturated phosphoric acid ester compound is less than 0.1%, the film-forming effect of positive and negative electrodes is poor, and the effect of improving performance cannot be achieved; and when its amount is too high, When it is greater than 2%, the thickness of the film formed at the electrode interface will be increased, the impedance of the battery will be increased, and the performance of the battery will be deteriorated.

At the same time, when the content of sulfone compounds is less than 0.1%, the sulfone compounds cannot effectively play a role; when the content of sulfone compounds is greater than 10%, in fact, within a certain range, such as below 30%, it can still show relatively strong good performance. When the content of the sulfone compound is greater than 30%, the viscosity of the electrolyte will be too high, and at the same time, a thick film will be formed on the electrode interface, which will increase the battery impedance and deteriorate the battery performance.

It should be noted that the key point of this application is to use unsaturated phosphate compounds and sulfone compounds in combination to improve high and low temperature performance and cycle performance; it can be understood that changes in the amount of the two will inevitably directly affect the performance of the electrolyte. Thus affecting the high and low temperature performance and cycle performance of the battery. Therefore, in the preferred solution of the present application, in order to ensure the performance of the electrolyte and the battery, the amounts of both are specifically limited. It can be understood that within the scope defined in the present application, the configured non-aqueous electrolyte has good high and low temperature performance and cycle performance; if it exceeds this range, its corresponding performance will inevitably be affected, but, for some requirements relatively In low or inferior use requirements, the high and low temperature performance or cycle performance of the battery can also be improved to a certain extent.

Further, in the non-aqueous electrolyte solution for lithium-ion batteries of the present application, the weight ratio of sulfone compounds to unsaturated phosphate compounds is greater than or equal to 0.2. When the content of unsaturated phosphate compounds is high and the content of sulfone compounds is low, the low temperature performance is obviously insufficient.

Preferably, the organic solvent of the non-aqueous electrolyte is at least one selected from ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate and propyl methyl carbonate.

Preferably, the lithium salt of the non-aqueous electrolyte is selected from lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium difluorooxalate borate, lithium bis(trifluoromethylsulfonyl)imide and lithium bisfluorosulfonylimide at least one of the salts.

Another aspect of the present application discloses a lithium-ion battery, including a positive electrode, a negative electrode, a separator placed between the positive electrode and the negative electrode, and an electrolyte, wherein the electrolyte is the non-aqueous electrolyte of the lithium-ion battery of the present application.

The charging cut-off voltage of the lithium ion battery of the present application is greater than or equal to 4.35V.

Preferably, in the lithium ion battery of the present application, the positive electrode is selected from LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiCo _{1-y My} O ₂ , LiNi _{1-y My} O ₂ , LiMn _{2-y My} O 2 ₄ and at least one of LiNi _x Co _y Mn _z M _1-xyz O ₂ ; wherein M is selected from Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, At least one of Sr, V and Ti, and 0≤y≤1, 0≤x≤1, 0≤z≤1, x+y+z≤1.

It should be noted that the non-aqueous electrolyte of the present application is developed for lithium-ion batteries, so it can be applied to various lithium-ion batteries, including but not limited to the types listed in this application.

Owing to adopting above technical scheme, the beneficial effect of the present application is:

In the non-aqueous electrolyte solution of the present application, the unsaturated phosphoric acid ester compound and the sulfone compound shown in Formula 1 are combined and added to the electrolyte solution at the same time to form a layer of uniform composition, moderate thickness, and good compactness on the electrode interface. Membrane; the combination of the two can make the electrolyte have good stability in the positive electrode, so that the battery can obtain excellent high-temperature performance and cycle performance, and can maintain a low impedance of the battery, so that the battery can obtain excellent low-temperature performance. The non-aqueous electrolyte of the present application has laid the foundation for the preparation of high-quality power batteries.

detailed description

The key point of this application is that the combination of the unsaturated phosphoric acid ester compound and the sulfone compound shown in formula 1 can be added to the non-aqueous electrolyte solution to keep the battery at a low temperature without affecting the high temperature performance and cycle performance. internal resistance, which in turn enables the battery to obtain excellent low-temperature performance.

Among them, the unsaturated phosphate compound represented by formula 1 can form a stable passivation film on the surface of the negative electrode, which can largely prevent the reduction and decomposition of the electrolyte. In addition, unsaturated phosphate compounds can also form a protective film on the surface of the positive electrode, which can further prevent the electrolyte from being oxidized and decomposed on the surface of the positive electrode, and at the same time inhibit the dissolution of positive metal ions, especially when the charging voltage is equal to or greater than 4.35V. The effect is more obvious, and the high-temperature performance and cycle performance of the lithium battery can be significantly improved, but the addition of the unsaturated phosphate compound of formula 1 also causes the internal resistance to increase, thereby deteriorating the low-temperature performance.

In view of the above problems, the present application adds sulfone compounds on the basis of adding unsaturated phosphoric acid ester compounds shown in Formula 1. Due to the low oxidation potential of sulfone compounds, a protective film with a thinner thickness, uniform composition and good compactness can be formed on the positive electrode. The good compactness of the protective film can effectively improve the decomposition reaction of the electrolyte at the positive electrode and prevent the dissolution of positive metal ions; the thickness of the protective film and the uniform composition can effectively reduce the impedance; and the reduction of the impedance can make the battery obtain excellent low temperature. performance.

Therefore, the beneficial effect of the lithium-ion battery non-aqueous electrolyte of the present application is:

(1) The unsaturated phosphate compound can form a dense passivation film on the positive electrode, so that the electrolyte has better stability, so that the battery has excellent high temperature performance and cycle performance. Sulfone compounds can also form a film on the electrode, and the formed film composition is uniform and dense, so that the battery has a lower impedance, so that the battery has excellent low-temperature performance.

(2) Combine the unsaturated phosphate compound shown in formula 1 and the sulfone compound, and add them to the electrolyte at the same time to form a protective film with uniform composition, moderate thickness and good compactness on the electrode interface; the combination of the two Using it can make the battery obtain excellent high-temperature performance and cycle performance, and the combination of the two can keep the battery at a low impedance, thereby enabling the battery to obtain excellent low-temperature performance.

In addition, in order to ensure the performance of the non-aqueous electrolyte, the present application limits the dosage of the unsaturated phosphoric acid ester compound and sulfone compound. Wherein, the sulfone compound accounts for 0.5%～30% of the total weight of the non-aqueous electrolyte of the lithium-ion battery, preferably, accounts for 1-10% of the total weight of the non-aqueous electrolyte of the lithium-ion battery. High chemical stability, give full play to the performance of the electrolyte. Moreover, in a preferred implementation of the present application, a cyclic sulfone compound and a chain sulfone compound are added at the same time, the two act synergistically, and the content of the cyclic sulfone compound is 1-3% of the total weight of the electrolyte. %, the content of chain sulfone compounds is 1-2% of the total weight of the electrolyte, and the synergistic effect of the two forms a protective film on the positive electrode with a relatively uniform thickness and good compactness, which can effectively reduce impedance and improve battery performance. .

The present application will be described in further detail below through specific examples. The following examples only further illustrate the present application, and should not be construed as limiting the present application.

Example 1

The preparation method of the lithium-ion battery in this example includes a positive electrode preparation step, a negative electrode preparation step, an electrolyte preparation step, a diaphragm preparation step and a battery assembly step. details as follows:

The positive electrode preparation steps are: mix the positive electrode active material LiNi _0.5 Co _0.2 Mn _0.3 O ₂ , conductive carbon black and binder polyvinylidene fluoride at a mass ratio of 96.8:2.0:1.2, and disperse them in N-methyl-2-pyrrolidone In the process, the positive electrode slurry is obtained, and the positive electrode slurry is evenly coated on both sides of the aluminum foil, after drying, calendering and vacuum drying, and after welding the aluminum lead wires with an ultrasonic welder, the positive electrode plate is obtained. The thickness of the electrode plate is 120 Between -150μm.

Negative electrode preparation steps are: mix graphite, conductive carbon black, binder styrene-butadiene rubber and carboxymethyl cellulose according to the mass ratio of 96:1:1.2:1.8, disperse in deionized water, obtain negative electrode slurry, and negative electrode slurry The material is coated on both sides of the copper foil, dried, calendered and vacuum-dried, and the nickel lead-out wire is welded with an ultrasonic welder to obtain a negative plate, and the thickness of the plate is between 120-150 μm.

Electrolyte preparation steps are: mix ethylene carbonate, ethyl methyl carbonate and diethyl carbonate in a volume ratio of EC:EMC:DEC=3:3:4, add lithium hexafluorophosphate with a concentration of 1.0mol/L after mixing, Based on the total weight of the electrolyte, 0.1 wt% of tripropargyl phosphate and 0.5 wt% of sulfolane were added.

The preparation step of the diaphragm is as follows: a three-layer separation film of polypropylene, polyethylene and polypropylene is used, and the thickness is 20 μm.

The battery assembly steps are: place a three-layer separator with a thickness of 20 μm between the positive electrode plate and the negative electrode plate, then wind the sandwich structure composed of the positive electrode plate, negative electrode plate and separator, and then flatten the winding body and put it into the In the square aluminum metal shell, the lead wires of the positive and negative electrodes were respectively welded on the corresponding positions of the cover plate, and the cover plate and the metal shell were welded together with a laser welding machine to obtain the battery cell to be injected; The electrolyte is injected into the cell through the liquid injection hole, and the amount of the electrolyte should ensure that the gap in the cell is filled.

Then carry out the routine formation of the first charge according to the following steps: 0.05C constant current charging for 3 minutes, 0.2C constant current charging for 5 minutes, 0.5C constant current charging for 25 minutes, shelving for 1 hour, shaping, replenishing liquid, sealing, and then further charging with 0.2C current Constant current charging to 4.2V, after 24 hours at room temperature, 0.2C constant current and constant voltage charging to 4.2V, and then 0.2C constant current discharge to 3.0V. Obtain the lithium-ion battery for this example.

The lithium-ion battery prepared in this example is tested as follows:

(1) High-temperature cycle performance test: At 45°C, the formed battery was charged to 4.35V with 1C constant current and constant voltage, and then discharged to 3.0V with 1C constant current. After 300 charge/discharge cycles, calculate the capacity retention rate of the 300th cycle to evaluate its high-temperature cycle performance. Calculated as follows:

The 300th cycle capacity retention rate (%)=(300th cycle discharge capacity/1st cycle discharge capacity)×100%.

(2) Cycling performance test at room temperature: At 25°C, the formed battery was charged to 4.35V with 1C constant current and constant voltage, and then discharged to 3.0V with 1C constant current. After 500 charge/discharge cycles, calculate the capacity retention rate of the 500th cycle to evaluate its normal temperature cycle performance. Calculated as follows:

The 500th cycle capacity retention rate (%) = (500th cycle discharge capacity / first cycle discharge capacity) × 100%;

(3) High-temperature storage performance: charge the formed battery to 4.35V at room temperature with 1C constant current and constant voltage, measure the initial discharge capacity of the battery, and then store it at 60°C for 30 days, discharge it at 1C to 3.0V, and measure the battery capacity Maintain capacity and restore capacity. Calculated as follows:

Battery capacity retention rate (%) = retention capacity/initial capacity × 100%;

Battery capacity recovery rate (%)=recovered capacity/initial capacity×100%.

(4) Low-temperature discharge performance test: At 25°C, the formed battery was charged to 4.35V with 1C constant current and constant voltage, and then discharged to 3.0V with 1C constant current, and the discharge capacity was recorded. Then it was fully charged with 1C constant current and constant voltage, placed in an environment of -20°C for 12 hours, and then discharged to 3.0V with a constant current of 1C, and the discharge capacity was recorded.

Low temperature discharge efficiency value at -20°C = 1C discharge capacity (-20°C)/1C discharge capacity (25°C).

(5) Normal and low temperature direct current impedance (DCIR) performance test: At 25°C, charge the formed battery 1C to a half-charged state, charge and discharge it with 0.1C, 0.2C, 0.5C, 1C and 2C for ten seconds, respectively. Record the charge and discharge cut-off voltage. Then, take the charge and discharge current of different rates as the abscissa (unit: A), and take the cut-off voltage corresponding to the charge and discharge current as the ordinate to make a linear relationship diagram (unit: mV).

Charging DCIR value = the slope value of the linear graph of different charging currents and corresponding cut-off voltages.

Discharge DCIR value = the slope value of the linear graph of different discharge currents and corresponding cut-off voltages.

(6) In addition, after charging the formed battery at 0°C with 0.3C, measure the degree of lithium deposition on the negative electrode, and use a 5-point scale for evaluation. The lower the score, the more serious the lithium deposition. Specifically, 5 points indicate no lithium analysis, 4 indicates slight lithium analysis, 3 indicates general lithium analysis, 2 indicates severe lithium analysis, and 1 indicates severe lithium analysis.

All test results of this example are shown in Table 3.

Example 2-20

In Examples 2-20, except that the specific compounds of the sulfone compound and the unsaturated phosphoric acid ester compound, and the amount thereof are different, the others are the same as in Example 1. The specific compounds of each embodiment and their dosage are shown in Table 2, wherein the dosage is calculated according to the percentage of each substance accounting for the total weight of the non-aqueous electrolyte of the lithium-ion battery.

In addition, the present application has also designed 6 comparative examples, i.e. comparative examples 1-6. Similarly, compared with Example 1 or other examples, the 6 comparative examples are only different in the specific compound and dosage added, and the others are all Same as Example 1. The specific compounds and their dosages of each comparative example are shown in Table 2. Similarly, the dosages are calculated according to the percentage of the added substances in the total weight of the non-aqueous electrolyte of the lithium-ion battery.

Table 2 each embodiment and the substance of comparative example and consumption thereof

In the table, a blank indicates that the corresponding example or comparative example does not add the corresponding substance. Tripropargyl phosphate is the compound 1 in Table 1, and diallyl ethyl phosphate is the compound 4 in Table 1.

The test results of Examples 1-20 and Comparative Examples 1-6 are shown in Table 3.

Table 3 each embodiment and the test result of comparative example

In Table 2, charging at 0°C and 0.3C, in the negative electrode lithium deposition test, 5 represents no lithium deposition, 4 represents slight lithium deposition, 3 represents normal lithium deposition, 2 represents severe lithium deposition, and 1 represents severe lithium deposition.

By comparing the test results of Comparative Examples 1-6, it can be found that when the unsaturated phosphate compound is used alone, the cycle performance and high-temperature storage are better, but the low-temperature performance is poor. When the sulfone compound is used alone, the cycle performance and high-temperature storage performance are poor, and the low-temperature performance is better.

In the test results of Examples 1-20 of the present application, through the comparison of Comparative Example 1 and Examples 3-5, 8-13, it can be found that adding sulfone compounds on the basis of unsaturated phosphoric acid ester compounds, not only Low temperature performance can be significantly improved, while cycle performance and high temperature performance are also significantly improved.

At the same time, in the test results of Examples 1-20 of the present application, compared with Comparative Examples 1-6, it can be found that the high-temperature performance and low-temperature performance of all examples containing unsaturated phosphoric acid ester compounds and sulfone compounds are different. improve. Through the comparison of Examples 4, 6, and 7, and the comparison between 17 and 19, with the increase of unsaturated phosphoric acid ester compounds, its high-temperature performance is improved, but the low-temperature performance is relatively reduced, especially the impedance. With the increase of the dosage, the impedance also increased. Especially when the content of unsaturated phosphate compounds is high and the content of sulfone compounds is low, the low temperature performance is obviously insufficient.

To sum up, this application uses unsaturated phosphate compounds and sulfone compounds in combination, and in an appropriate ratio, the battery can obtain excellent high-temperature performance, cycle performance and good low-temperature performance. Among them, in terms of dosage, the dosage of unsaturated phosphates is 0.1% to 2%, and the dosage of sulfone compounds is 0.1% to 30%, which can improve the high and low temperature performance and cycle performance; The effect is better when the amount of sulfone compound is 1% to 10%.

The above content is a further detailed description of the present application in conjunction with specific implementation modes, and it cannot be considered that the specific implementation of the present application is limited to these descriptions. For those of ordinary skill in the technical field to which this application belongs, some simple deduction or substitutions can be made without departing from the concept of this application, which should be deemed to belong to the protection scope of this application.

Claims (9)

1. a kind of non-aqueous electrolyte for lithium ion cell it is characterised in that: include unsaturated phosphate compounds and sulfone class chemical combination Thing, described sulfone compound includes ring-type sulfone compound and/or straight chain sulfone compound；

Described unsaturation phosphate compounds have structure shown in formula one,

Wherein, r₁、r₂、r₃Separately it is selected from the alkyl that carbon number is 1-4, and r₁、r₂、r₃In at least one is containing double Key or the unsaturated alkyl of three key；

Described ring-type sulfone compound has structure shown in formula two, and described straight chain sulfone compound has structure shown in formula three,

Wherein, r₄、r₅、r₆、r₇Separately it is selected from the alkyl that hydrogen atom, halogen or carbon number are 1-5, a is including 2～6 The substituted or non-substituted alkylidene of individual carbon number, the functional group that it replaces is halogen or carbon number is the alkyl of 1-3.

2. non-aqueous electrolyte for lithium ion cell according to claim 1 it is characterised in that: described ring-type sulfone compound is Formula four and/or at least one of structural compounds shown in formula five,

Wherein, r₈-r₁₆Separately it is selected from the alkyl that hydrogen atom, halogen or carbon number are 1-5.

3. non-aqueous electrolyte for lithium ion cell according to claim 1 it is characterised in that: described sulfone compound be selected from ring In fourth sulfone, 3- methyl sulfolane, 3,3,4,4- tetrafluoro sulfolane, ring penta sulfone, dimethyl sulfone, Methylethyl sulfone and diethyl sulfone At least one.

4. the non-aqueous electrolyte for lithium ion cell according to any one of claim 1-3 it is characterised in that: described unsaturation phosphorus Acid esters compound accounts for the 0.1%～2% of non-aqueous electrolyte for lithium ion cell gross weight it is preferred that to account for lithium ion battery non-aqueous The 0.2%～1% of electrolyte gross weight.

5. the non-aqueous electrolyte for lithium ion cell according to any one of claim 1-3 it is characterised in that: described sulfone class chemical combination Thing accounts for the 0.1%～30% of non-aqueous electrolyte for lithium ion cell gross weight it is preferred that accounting for non-aqueous electrolyte for lithium ion cell gross weight The 0.1～10% of amount, it is further preferred that accounting for the 0.5～10% of non-aqueous electrolyte for lithium ion cell gross weight, it is furthermore preferred that Account for the 1～10% of non-aqueous electrolyte for lithium ion cell gross weight.

6. the non-aqueous electrolyte for lithium ion cell according to any one of claim 1-3 it is characterised in that: described sulfone class chemical combination Thing with described unsaturation phosphate compounds weight than more than or equal to 0.2.

7. a kind of lithium ion battery, including positive pole, negative pole, the barrier film being placed between positive pole and negative pole, and electrolyte, its feature It is: described electrolyte is the non-aqueous electrolyte for lithium ion cell described in any one of claim 1-6.

8. lithium ion battery according to claim 7 it is characterised in that: described positive pole be selected from licoo₂、linio₂、 limn₂o₄、lico_1-ym_yo₂、lini_1-ym_yo₂、limn_2-ym_yo₄And lini_xco_ymn_zm_1-x-y-zo₂One of or two or more, Wherein, m is selected from one of fe, co, ni, mn, mg, cu, zn, al, sn, b, ga, cr, sr, v and ti or two or more, and 0≤ Y≤1,0≤x≤1,0≤z≤1, x+y+z≤1.

9. lithium ion battery according to claim 7 it is characterised in that: the charge cutoff voltage of described lithium ion battery is big In or be equal to 4.35v.