CN104638293A - High-compaction-density cathode lithium ion battery and electrolyte - Google Patents

Abstract

The application discloses a high compacted density negative electrode lithium ion battery and electrolyte solution. The high compacted density negative electrode lithium ion battery of the present application comprises a positive electrode, a negative electrode, a diaphragm and an electrolyte solution, the electrolyte solution contains 1-5% of the total weight of the electrolyte solution of alkyl sultone, 1-10% of fluoroethylene carbonate Ester, 0.1-2% vinyl ethylene carbonate; the compacted density of the negative electrode is not less than 1.65g/cm ³ . The lithium-ion battery of the present application has added an appropriate amount of alkyl sultone, fluoroethylene carbonate and vinyl vinyl carbonate in its electrolyte, so that the battery can adopt a negative electrode with a higher compaction density, thereby having a larger volume capacity density. Moreover, the battery of the present application is easy to infiltrate, can ensure no lithium precipitation, has long cycle life at normal temperature and good storage performance at high temperature; it lays a foundation for the expanded application of lithium ion batteries.

Description

A kind of high compacted density negative electrode lithium-ion battery and electrolyte

technical field

The present application relates to the field of lithium ion batteries with high compacted density negative electrodes, in particular to a high compacted density negative electrode lithium ion battery and an electrolyte solution adapted thereto.

Background technique

In recent years, portable electronic products, such as cameras, digital video cameras, mobile phones, notebook computers, etc., have been widely used in people's daily life. Reducing size, reducing weight, and prolonging service life are the development trends and requirements of the electronic product industry. Therefore, it is an urgent need for the development of the industry to develop power supply products that are compatible with portable electronic products, especially the development of lightweight secondary batteries that can provide high energy density.

Improving the compaction density is one of the important means to increase the energy density of the lithium-ion battery anode. However, the higher the compaction density of the negative electrode material of lithium-ion batteries, the higher the requirements for the electrolyte. The electrolyte suitable for conventional compacted negative electrodes is prone to a series of problems such as incomplete infiltration, lithium deposition in the battery, reduced cycle life, and reduced rate performance in a high-pressure compacted system. At present, there are two ways to improve the performance of the high-pressure negative electrode electrolyte. One is to add low-viscosity solvents, such as ethyl acetate, etc. These solvents can reduce the viscosity of the electrolyte, promote the infiltration of the electrolyte, and increase the cycle rate of the battery. Performance; one is to add additives that promote circulation and reduce impedance, such as FEC, etc. These additives will reduce the impedance of the battery, and the battery is not easy to decompose lithium, which is beneficial to the improvement of the cycle life of the battery. However, these two methods will reduce the high-temperature stability of the battery, resulting in poor high-temperature performance of the electrolyte and easy gas inflation. Therefore, ensuring that the battery does not decompose lithium, and taking into account the high-temperature performance and normal temperature cycle of the battery is a major topic in the research of high-pressure negative lithium-ion battery electrolyte.

Contents of the invention

The purpose of this application is to provide a lithium-ion battery with a high compacted density negative electrode, and an electrolyte solution compatible therewith.

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

One aspect of the present application discloses a lithium-ion battery with a high compacted density negative electrode, comprising a positive electrode, a negative electrode, a separator and an electrolyte, wherein the electrolyte contains 1-5% of alkyl sultones accounting for the total weight of the electrolyte 1-10% of fluoroethylene carbonate in the total weight of the electrolyte, 0.1-2% of vinyl ethylene carbonate in the total weight of the electrolyte; and the compacted density of the negative electrode is not less than 1.65g/cm ³ .

It should be noted that the high compacted density negative electrode lithium ion battery of the present application can still ensure that the battery does not decompose lithium when the compacted density of the negative pole piece is not less than 1.65g/ ^cm3 , and has a good battery capacity. High temperature performance and normal temperature cycle performance; one of the important reasons is creatively adding 1-5% of the total weight of the electrolyte to the alkyl sultone and 1-10% of the total weight of the electrolyte to the conventional electrolyte. Ethylene carbonate and vinyl ethylene carbonate accounting for 0.1-2% of the total weight of the electrolyte; it can be understood that in the battery of the application, for example, other components of the electrolyte, diaphragm, positive pole and negative pole, etc., can refer to conventional Lithium-ion battery; as long as the additives in the electrolyte solution are added in the amount limited by the application, the effect of the application can be achieved.

Preferably, the compacted density of the pole piece of the negative electrode is not less than 1.70 g/cm ³ . It should be noted that, in the lithium-ion battery of the present application, the compacted density of the pole piece of the negative electrode can reach more than 1.70 g/cm ³ , thereby preparing a lithium-ion battery with a higher energy density; and, at such a high compacted density In the case of the negative electrode, it can still ensure that the battery does not decompose lithium, and has good battery high temperature performance and normal temperature cycle performance.

Preferably, in the lithium-ion battery of the present application, the electrolyte also contains 0.1-2% of cyclic phosphoric anhydride accounting for the total weight of the electrolyte, and the cyclic phosphoric anhydride has the structure shown in formula 1;

Wherein R1, R2, R3 can be independently selected from H or alkyl, haloalkyl, alkenyl or alkynyl with 1-6 carbon atoms repeatedly.

More preferably, cyclic phosphoric anhydride is at least one of the compounds shown in structural formula 1, structural formula 2, structural formula 3 and structural formula 4;

Preferably, the electrolyte of the lithium ion battery of the present application further contains 1-20% of fluorobenzene accounting for the total weight of the electrolyte.

Preferably, in order to achieve a better effect, in the lithium ion battery of the present application, the active material of the positive electrode is lithium cobalt oxide, and the active material of the negative electrode is graphite.

Preferably, in order to achieve a better effect, in the lithium ion battery of the present application, the organic solvent of the electrolyte is a mixed solvent composed of ethylene carbonate, diethyl carbonate and ethyl methyl carbonate, the electrolyte is lithium hexafluorophosphate, and the volume ratio Ethylene carbonate: diethyl carbonate: ethyl methyl carbonate = 1:1:1.

The other side of the application also discloses an electrolyte solution compatible with the high compacted density negative electrode lithium-ion battery of the application, in which the electrolyte solution contains 1-5% of alkyl sultones accounting for the total weight of the electrolyte solution, The fluoroethylene carbonate accounts for 1-10% of the total weight of the electrolyte, and the vinyl ethylene carbonate accounts for 0.1-2% of the total weight of the electrolyte.

It should be noted that the electrolyte of the present application is due to the addition of alkyl sultones accounting for 1-5% of the total weight of the electrolyte, accounting for 1-10% of the total weight of the electrolyte fluoroethylene carbonate, and accounting for 1-5% of the total weight of the electrolyte. 0.1-2% vinyl ethylene carbonate by weight; it can be applied to lithium-ion batteries with higher compaction density negative electrodes, so that the prepared batteries can ensure that lithium is not separated, and also have good battery high temperature performance and normal temperature cycle performance; laid the foundation for the preparation of lithium-ion batteries with high energy density.

Preferably, the electrolyte also contains cyclic phosphoric anhydride accounting for 0.1-2% of the total weight of the electrolyte, and the cyclic phosphoric anhydride has the structure shown in formula 1;

Wherein R1, R2, R3 can be independently selected from H or alkyl, haloalkyl, alkenyl or alkynyl with 1-6 carbon atoms repeatedly.

More preferably, at least one of the cyclic phosphoric anhydrides represented by structural formula 1, structural formula 2, structural formula 3 and structural formula 4 is added to the electrolyte.

Preferably, the electrolyte also contains 1-20% of fluorobenzene accounting for the total weight of the electrolyte.

Preferably, in order to achieve a better effect, the electrolyte solution of the present application, its organic solvent is a mixed solvent composed of ethylene carbonate, diethyl carbonate and ethyl methyl carbonate, the electrolyte is lithium hexafluorophosphate, and ethylene carbonate: diethyl carbonate Ethyl ester: ethyl methyl carbonate = 1:1:1.

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

In the high compacted density negative electrode lithium ion battery of the present application, 1-5% by weight of alkyl sultone, 1-10% by weight of fluoroethylene carbonate and 0.1-2% by weight are added to the electrolyte The proportion of vinyl ethylene carbonate allows the battery to use a negative electrode with a higher compaction density, thereby having a larger volumetric capacity density. Moreover, the high compacted density negative electrode lithium ion battery of the present application is easy to infiltrate, not only can ensure that lithium is not separated, but also has good battery high temperature performance and normal temperature cycle performance; it has laid a foundation for the expanded application of lithium ion batteries.

Detailed ways

The ultimate purpose of this application is to provide a high-pressure negative lithium-ion battery that is easy to infiltrate, does not decompose lithium, has good cycle life at room temperature, good high-temperature safety, and excellent comprehensive performance. To achieve this goal, the electrolyte of lithium-ion batteries is an important factor. For this reason, the present application creatively added an appropriate amount of alkyl sultone (1,3-PS), fluoroethylene carbonate (FEC) and vinyl ethylene carbonate (VEC) in the electrolyte of the lithium-ion battery, In order to improve the performance of the electrolyte; thereby preparing a high-pressure negative electrode lithium-ion battery with a negative electrode compacted density greater than 1.65g/cm ³ , even greater than 1.70g/cm ³ , and can also ensure that the battery does not decompose lithium, and It has good battery high temperature performance and normal temperature cycle performance. The high compacted density negative electrode lithium ion battery of the present application not only has higher energy density, but also has improved comprehensive properties such as high temperature performance and normal temperature cycle performance.

On the basis of the high compacted density negative electrode lithium ion battery of the present application, the present application also provides a kind of electrolytic solution adapted thereto, and the preferred scheme of this electrolytic solution is, in the organic solvent is ethylene carbonate, diethyl carbonate A mixed solvent composed of ethyl methyl carbonate, the electrolyte is lithium hexafluorophosphate, and on the basis of ethylene carbonate: diethyl carbonate: ethyl methyl carbonate = 1:1:1, add 1-5% of the total weight of the electrolyte Alkyl sultones, fluoroethylene carbonate accounting for 1-10% of the total weight of the electrolyte and vinyl ethylene carbonate accounting for 0.1-2% of the total weight of the electrolyte. Among them, alkyl sultone (1,3-PS) can form a stable solid electrolyte interface film on the negative electrode, that is, SEI, which has a significant effect on inhibiting high-temperature gas expansion and improves the safety of the battery; fluoroethylene carbonate ( FEC) can improve the cycle life of the battery; vinyl ethylene carbonate (VEC) can form a film on the positive and negative electrodes to improve the oxidation stability of the electrolyte, and the film formation on the negative electrode can also improve the high temperature performance and cycle life of the battery; The sultone, fluoroethylene carbonate and vinyl ethylene carbonate are used together, so that the electrolyte can be adapted to a lithium-ion battery with a negative electrode of higher compaction density.

Preferably, cyclophosphoric anhydride and fluorobenzene are added to the electrolyte, and the cyclophosphoric anhydride accounts for 0.1-2% of the total weight of the electrolyte, and fluorobenzene accounts for 1-20% of the total weight of the electrolyte. Among them, on the one hand, cyclic phosphoric anhydride can improve the high-temperature stability of the electrolyte and significantly improve the high-temperature safety of the battery. When its content is less than 0.1%, the effect is not obvious, and when its content is higher than 2%, it increases the impedance of the negative electrode of the battery, resulting in Analyze lithium. Fluorobenzene can reduce the viscosity of the electrolyte and the surface tension between the pole pieces, and promote infiltration. When the content is less than 1%, the effect is not obvious. When the content is more than 20%, the high-temperature stability of the electrolyte is reduced, which is not conducive to the high-temperature safety of the battery. .

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

In this example, a mixed organic solvent composed of vinyl ester (EC), diethyl carbonate (DEC) and ethyl methyl carbonate (EMC), and lithium hexafluorophosphate (LiPF ₆ ) were used as the basic electrolyte for testing. Among the additives, cyclic phosphoric anhydrides with four structures of structural formula 1 to structural formula 4 were selectively added for testing.

This example has designed 18 test groups and 3 control groups altogether, and the consumption of each additive in test group and control group is as shown in table 1; Except the difference shown in table 1, each test group and other designs of control group are completely same. details as follows:

1) Preparation of electrolyte

Mix ethylene carbonate (EC), diethyl carbonate (DEC) and ethyl methyl carbonate (EMC) in a mass ratio of EC:DEC:EMC=1:1:1, and then add lithium hexafluorophosphate (LiPF ₆ ) to mol The concentration is 1mol/L, and then add each additive according to Table 1. The amount of the additive is calculated as a percentage of the total mass of the electrolyte.

2) Preparation of positive plate

Mix positive electrode active material lithium cobaltate, conductive carbon black Super-P and binder polyvinylidene fluoride (PVDF) by the mass ratio of 93:4:3, then they are dispersed in N-methyl-2-pyrrolidone ( NMP) to obtain positive electrode slurry. The slurry is evenly coated on both sides of the aluminum foil, dried, calendered and vacuum-dried, and the aluminum lead-out wire is welded with an ultrasonic welder to obtain a positive plate, the thickness of which is 120-150 μm.

3) Preparation of negative plate

Mix negative electrode active material modified natural graphite, conductive carbon black Super-P, binder styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) at a mass ratio of 94:1:2.5:2.5, and then disperse them In deionized water, negative electrode slurry was obtained. The slurry is coated on both sides of the copper foil, dried, rolled, and nickel-made lead wires are welded by an ultrasonic welder to obtain a negative plate. The compacted densities of each test group and control group after rolling are shown in Table 1.

4) Preparation of batteries

A polyethylene microporous membrane with a thickness of 20 μm is placed between the positive plate and the negative plate as a separator, and then the sandwich structure composed of the positive plate, negative plate and separator is wound, and then the wound body is flattened and placed in an aluminum plastic In the film, after the lead-out wires of the positive and negative electrodes are respectively drawn out, the aluminum-plastic film is heat-pressed and sealed to obtain the battery cell to be injected.

5) Injection and formation of batteries

In a glove box with a dew point controlled below -40°C, inject the electrolyte solution prepared above into the cell through the liquid injection hole, and the amount of electrolyte should ensure that the gap in the cell is filled. Then carry out the formation according to the following steps: 0.05C constant current charging for 180min, 0.1C constant current charging for 180min, after 24hrs resting for shaping and sealing, and then further charging at 0.2C constant current to 4.2V, after standing at room temperature for 24hrs, using 0.2C Current constant current discharge to 3.0V.

6) Normal temperature cycle performance test

At room temperature, charge with a constant current of 0.5C to 4.2V, then charge with a constant voltage until the current drops to 0.1C, and then discharge with a constant current of 0.5C to 3.0V, and cycle for 200 cycles, and record the discharge in the first week Capacity and the discharge capacity of the 200th week, the capacity retention rate is calculated according to the following formula:

Capacity retention rate = (discharge capacity of the 200th cycle ÷ discharge capacity of the first cycle) × 100%

The test results are shown in Table 2.

7) High temperature storage performance test

Charge the battery at room temperature with a constant current of 0.5C to 4.2V, then charge it at a constant voltage until the current drops to 0.1C, measure the thickness of the battery, and then store the battery in an oven with a constant temperature of 85°C for 4 hours. After taking it out, let the battery cool down to At room temperature, measure the thickness of the battery, and calculate the thickness expansion rate of the battery according to the following formula:

Thickness expansion rate = (battery thickness after storage - battery thickness before storage) ÷ battery thickness before storage × 100%

The test results are shown in Table 2.

The dosage and compacted density of each component of the electrolyte additive in table 1

test Compaction density FEC 1,3-PS VEC Cyclic Phosphoric Anhydride Fluorobenzene Test group 1 1.70g/ ^cm3 5% 3% 1% — — Test group 2 1.70g/ ^cm3 1% 3% 1% — — Test group 3 1.70g/ ^cm3 10% 3% 1% — — Test group 4 1.70g/ ^cm3 5% 1% 1% — — Test group 5 1.70g/ ^cm3 5% 5% 1% — —

Test group 6 1.70g/ ^cm3 5% 3% 0.1% — — Test group 7 1.70g/ ^cm3 5% 3% 2% — — Test group 8 1.70g/ ^cm3 5% 3% 1% Structural Formula 1: 0.1% — Test group 9 1.70g/ ^cm3 5% 3% 1% Structural formula 1:1% — Test group 10 1.70g/ ^cm3 5% 3% 1% Structural Formula 1: 2% — Test group 11 1.70g/ ^cm3 5% 3% 1% — 1% Test group 12 1.70g/ ^cm3 5% 3% 1% — 10% Test group 13 1.70g/ ^cm3 5% 3% 1% — 20% Test group 14 1.70g/ ^cm3 5% 3% 1% Structural Formula 1: 0.5% 5% Test group 15 1.70g/ ^cm3 5% 3% 1% Structural formula 2: 0.5% 5% Test group 16 1.70g/ ^cm3 5% 3% 1% Structural formula 3: 0.5% 5% Test group 17 1.65g/ ^cm3 5% 3% 1% Structural Formula 1: 0.5% 5% Test group 18 1.5g/ ^cm3 5% 3% 1% Structural Formula 1: 0.5% 5% Control group 1 1.70g/ ^cm3 — — — — — Control group 2 1.5g/ ^cm3 — — — — —

Table 2 Capacity retention rate and thickness expansion rate test results

test Capacity retention Thickness Expansion Test group 1 91.08% 4.32% Test group 2 85.34% 1.62% Test group 3 92.68% 9.48% Test group 4 91.65% 5.08% Test group 5 90.04% 3.24% Test group 6 92.51% 8.47% Test group 7 89.87% 1.82% Test group 8 91.03% 4.28% Test group 9 90.21% 1.96% Test group 10 88.61% 1.27% Test group 11 91.35% 4.58% Test group 12 92.33% 7.89% Test group 13 92.89% 12.16% Test group 14 91.52% 2.67% Test group 15 91.36% 2.53% Test group 16 91.48% 2.19% Test group 17 91.82% 2.87% Test group 18 92.08% 3.01% Control group 1 80.36% 9.35% Control group 2 91.54% 13.26%

It can be seen from the control group that on the basis of the same electrolyte, the normal temperature cycle performance of the battery with a negative electrode compacted density of 1.70g/ ^cm3 is significantly inferior to that of the battery with a compacted density of 1.50g/ ^cm3 , because the compacted density of the battery is too large , the electrolyte is prone to incomplete infiltration and lithium precipitation, resulting in increased battery impedance and poor cycle performance. From the test groups 14, 17, and 18, it can be seen that the high-pressure negative electrode lithium-ion battery prepared by using the electrolyte of the additive of the present application has basically no change in the normal temperature cycle performance of the battery with the increase of the negative electrode compaction density. From test groups 14, 15, and 16, it can be seen that among the additives of the present application, structural formula 1-structural formula 3 all have the same effect.

In addition, the thickness expansion rate of test group 13 is relatively high, which is believed to be due to the large amount of fluorobenzene used in test group 13. In this regard, this application has carried out in-depth research on the amount of fluorobenzene based on test group 13, and the results show that its content When the content is less than 1%, the effect is not obvious, and when the content is greater than 20%, the high-temperature stability of the electrolyte is reduced, which is not conducive to the high-temperature safety of the battery, such as test groups 11-13. The capacity retention rate of test group 2 is lower than other test groups because the amount of FEC is relatively small. The results of the research on the amount of FEC based on this test group show that the amount of FEC accounts for 1-10% of the total electrolyte weight. To meet the use requirements, about 5% is better, and when the dosage reaches 10%, it may affect the thickness expansion rate, such as test group 3. In addition, the thickness expansion rate of test group 6 is relatively high, which may be due to the low amount of VEC. Based on this, the results of the test on the amount of VEC show that the amount of VEC accounting for 0.1-2% of the total electrolyte weight can meet the use requirements. The amount of alkyl sultone accounts for 1-5% of the total weight of the electrolyte can achieve good results, such as test group 4 and test group 5. The amount of cyclic phosphoric anhydride accounts for 0.1-2% of the total weight of the electrolyte can achieve good results, such as test groups 8, 9 and 10.

For cyclic phosphoric anhydride, the structural formula 1-structural formula 4 adopted in the embodiment of the application is the application of four kinds of specific structures of formula 1. It can be understood that except structural formula 1-structural formula 4, other similar to these four structural formulas have Cyclic phosphoric anhydrides of formula 1, for example, R1, R2, R3 can be repeatedly selected from H or alkyl, haloalkyl, alkenyl or alkynyl with 1-6 carbon atoms, etc., can be used in this application.

In summary, in the lithium ion battery of the present application, the effective dosage of each additive component of its electrolytic solution is, alkyl sultone 1-5%, fluoroethylene carbonate 1-10%, vinyl ethylene carbonate Esters 0.1-2%; Among them, although 1% and 10% of fluoroethylene carbonate can meet the use requirements, the better solution is about 5%; the amount of vinyl ethylene carbonate can also be 0.1% and 2%. Satisfied for use, but the better solution is about 1%. In addition, it is also possible to selectively add at least one of cyclic phosphoric anhydride and fluorobenzene, the amount of cyclic phosphoric anhydride is 0.1-2%, and the amount of fluorobenzene is 1-20%; wherein, the amount of cyclic phosphoric anhydride is 0.1% and 2% can meet the use requirements, but the preferred solution is 0.5-1%; the effect is better when the amount of fluorobenzene is greater than or equal to 1% and less than 20%, although it also has a certain effect when the amount is 20% , but compared with other dosages, the effect is poor, and the optimal dosage is 1-5%.

In the high compacted density negative electrode lithium ion battery of the present application, additives of various components are added to the electrolyte, so that the electrolyte can meet the needs of the lithium ion battery of the high compacted density negative electrode, so that the lithium ion battery of the present application It has a larger volumetric capacity density; and due to the improved electrolyte, the lithium-ion battery of the present application is easy to infiltrate, which can not only ensure that lithium is not separated, but also has a long cycle life at room temperature and good high-temperature storage performance, and has good high-temperature performance of the battery and normal temperature cycle performance.

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 (10)

1. A lithium-ion battery with a high compacted density negative pole, comprising positive pole, negative pole, diaphragm and electrolyte, is characterized in that: the alkyl sultone accounting for 1-5% of the total weight of electrolyte is contained in the electrolyte, Fluoroethylene carbonate accounting for 1-10% of the total weight of the electrolyte, vinyl ethylene carbonate accounting for 0.1-2% of the total weight of the electrolyte; and, the compacted density of the negative electrode is not less than 1.65g/cm ³ . 2 . The lithium ion battery according to claim 1 , wherein the compacted density of the negative electrode is not less than 1.70 g/cm ³ . 3. The lithium ion battery according to claim 2, characterized in that: the electrolyte also contains cyclic phosphoric anhydride accounting for 0.1-2% of the total weight of the electrolyte, and the cyclophosphoric anhydride has a structure shown in formula 1; Wherein R1, R2, R3 can be independently selected from H or alkyl, haloalkyl, alkenyl or alkynyl with 1-6 carbon atoms repeatedly. 4. The lithium ion battery according to claim 3, characterized in that: the cyclic phosphoric anhydride is at least one of the compounds shown in structural formula 1, structural formula 2, structural formula 3 and structural formula 4; 5. The lithium ion battery according to claim 2, characterized in that: the electrolyte also contains 1-20% of fluorobenzene accounting for the total weight of the electrolyte. 6 . The lithium ion battery according to claim 1 , wherein the active material of the positive electrode is lithium cobaltate, and the active material of the negative electrode is graphite. 7. according to the lithium ion battery described in any one of claim 1-5, it is characterized in that: the organic solvent of described electrolytic solution is the mixed solvent that ethylene carbonate, diethyl carbonate and methyl ethyl carbonate form, and electrolyte is Lithium hexafluorophosphate, and ethylene carbonate: diethyl carbonate: ethyl methyl carbonate = 1:1:1. 8. An electrolytic solution for a high compacted density negative electrode lithium ion battery, characterized in that: the electrolytic solution contains alkyl sultones accounting for 1-5% of the total weight of the electrolytic solution, accounting for 1% of the total weight of the electrolytic solution - 10% of fluoroethylene carbonate, 0.1-2% of vinyl ethylene carbonate in the total weight of the electrolyte. 9. The electrolytic solution according to claim 8, characterized in that: the electrolytic solution also contains cyclic phosphoric anhydride accounting for 0.1-2% of the total weight of the electrolytic solution, and the cyclic phosphoric anhydride has a structure shown in formula 1; Wherein R1, R2, R3 can be independently selected from H or alkyl, haloalkyl, alkenyl or alkynyl with 1-6 carbon atoms repeatedly. 10. The electrolytic solution according to claim 8, characterized in that: said electrolytic solution also contains 1-20% of fluorobenzene accounting for the total weight of the electrolytic solution.