阅读说明：本技术 一种双离子电池用电解液及其制备方法 (Electrolyte for double-ion battery and preparation method thereof ) 是由 邵俊华 李海杰 张利娟 孔东波 王郝为 郭飞 闫国锋 宋东亮 王亚洲 侯红歧 谢 于 2021-08-27 设计创作，主要内容包括：本发明公开了一种双离子电池用电解液及其制备方法,包括锂盐、氟盐、溶剂与添加剂；所述溶剂为直链或支链羧酸酯；所述氟盐包括六氟环三磷腈。由于上述组分之间的协同作用,降低了电解液的粘度,而较低的电解液粘度,又能够加快放电过程中氟盐中的氟离子与锂盐中的锂离子形成氟化锂,从而形成双离子电池,并提升电池的循环性能。(The invention discloses an electrolyte for a double-ion battery and a preparation method thereof, wherein the electrolyte comprises lithium salt, villiaumite, a solvent and an additive; the solvent is linear chain or branched chain carboxylic ester; the fluoride salt comprises hexachlorocyclotriphosphazene. Due to the synergistic effect of the components, the viscosity of the electrolyte is reduced, the viscosity of the electrolyte is lower, and the formation of lithium fluoride from fluorine ions in fluorine salt and lithium ions in lithium salt in the discharging process can be accelerated, so that the double-ion battery is formed, and the cycle performance of the battery is improved.)

1. An electrolyte for a bi-ion battery, characterized in that:

comprises lithium salt, fluorine salt, solvent and additive;

the solvent is linear chain or branched chain carboxylic ester;

the fluoride salt comprises hexachlorocyclotriphosphazene;

the viscosity of the electrolyte for the double-ion battery is 0.8-1.50mpa · s.

2. The electrolyte for a bi-ion battery as recited in claim 1, wherein:

the concentration of the lithium salt is 0.05-0.10 mol/L.

3. The electrolyte for a bi-ion battery as recited in claim 1, wherein:

the lithium salt comprises at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium difluorooxalate phosphate and lithium tetrafluoroborate, lithium difluorooxalate borate, lithium bistrifluoromethylsulfonyl imide, lithium bistrifluoromethylimide, lithium bistrifluorosulfonimide and lithium perchlorate.

4. The electrolyte for a bi-ion battery as recited in claim 1, wherein:

the additive comprises modified N, N' -carbonyldiimidazole.

5. The electrolyte for a bi-ion battery as recited in claim 1, wherein:

the linear or branched carboxylic acid ester has the following structural formula:

wherein R1 and R2 are independently selected from substituted or unsubstituted C_1-7Alkyl, the substituents being selected from halogen;

6. the electrolyte for a bi-ion battery as recited in claim 1, wherein:

the mass ratio of the lithium salt, the villiaumite, the solvent and the additive is 2.3-4.6: 1.5-2.5: 50-78: 0.7-1.5.

7. The electrolyte for a bi-ion battery as recited in claim 1, wherein:

the additive further comprises at least one of polytetrafluoroethylene, acetylene black and propyl propionate.

8. The electrolyte for a bi-ion battery as recited in claim 1, wherein:

the additive also includes dimethyl sulfonate.

9. A method of preparing an electrolyte for a bi-ion battery as claimed in any one of claims 1 to 7, characterized in that: the method comprises the following steps:

and dispersing lithium salt, fluorine salt and an additive in a solvent, and stirring to obtain the electrolyte for the double-ion battery.

10. A lithium ion battery comprising a positive electrode sheet containing a positive electrode active material, a negative electrode sheet containing a negative electrode active material, a lithium battery separator, and the electrolyte for a bi-ion battery according to any one of claims 1 to 7.

Technical Field

The invention belongs to the technical field of electrolyte, and particularly relates to electrolyte for a dual-ion battery and a preparation method thereof.

Background

A lithium ion battery is a type of rechargeable battery that mainly relies on lithium ions moving between a positive electrode and a negative electrode to operate. During charging and discharging, Li⁺Intercalation and deintercalation to and from two electrodes: upon charging, Li⁺The lithium ion battery is taken out from the positive electrode and is inserted into the negative electrode through the electrolyte, and the negative electrode is in a lithium-rich state; the opposite is true during discharge. The lithium ion battery has the advantages of high specific energy, high charge-discharge efficiency, long service life and the like, and is one of the most promising chemical power sources at present.

However, the above-mentioned electrolyte in the lithium ion battery has the disadvantages of high price, high viscosity, poor battery rate characteristics, etc., and the method of reducing viscosity by using the combined action of the soluble liquid such as fluorinated ether and TFSI has poor thermal stability and is easy to swell, and the problem that the viscosity of the electrolyte is high and the battery performance is affected cannot be effectively solved.

Disclosure of Invention

The first technical problem to be solved by the invention is as follows:

an electrolyte for a bi-ion battery is provided.

The second technical problem to be solved by the invention is:

provides a preparation method of the electrolyte for the double-ion battery.

The third technical problem to be solved by the invention is:

the application of the electrolyte for the double-ion battery is disclosed.

In order to solve the first technical problem, the invention adopts the technical scheme that:

an electrolyte for a dual-ion battery,

comprises lithium salt, fluorine salt, solvent and additive;

the solvent is linear chain or branched chain carboxylic ester;

the fluoride salt comprises hexachlorocyclotriphosphazene;

the viscosity of the electrolyte for the double-ion battery is 0.8-1.50mpa · s.

According to one embodiment of the present invention, the concentration of the lithium salt is 0.05 to 0.10 mol/L.

According to an embodiment of the present invention, the lithium salt includes at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium difluorooxalato phosphate and lithium tetrafluoroborate, lithium difluorooxalato borate, lithium bistrifluoromethylsulfonyl imide, lithium bistrifluoromethylimide, lithium bistrifluorosulfonylimide, lithium perchlorate.

According to one embodiment of the invention, the additive comprises a modified N, N' -carbonyldiimidazole.

The preparation method of the modified N, N' -carbonyl diimidazole comprises the following steps:

mixing N 'N-carbonyl diimidazole with ethyl chloride, and stirring to obtain chloride salt of ethyl grafted N' N-carbonyl diimidazole;

and (2) mixing the chloride salt of the ethyl grafted N ', N ' -carbonyldiimidazole, sodium dicyanamide and acetone, stirring, adding ethanolamine, and performing nucleophilic addition reaction between carbonyl and hydroxyl to obtain the modified N, N ' -carbonyldiimidazole.

According to one embodiment of the present invention, the above-mentioned linear or branched carboxylic acid ester contains the following structural formula:

wherein R1 and R2 are independently selectedFrom substituted or unsubstituted C_1-7Alkyl, the substituents being selected from halogen;

according to one embodiment of the present invention, the mass ratio of the lithium salt, the fluorine salt, the solvent and the additive is 2.3 to 4.6: 1.5-2.5: 50-78: 0.7-1.5.

According to an embodiment of the present invention, the additive further comprises at least one of polytetrafluoroethylene, acetylene black, and propyl propionate.

According to an embodiment of the present invention, the additive further comprises dimethyl sulfonate.

The dimethyl sulfonate can inhibit the linear chain or branched chain carboxylic ester from continuously generating oxidation reaction at the anode under high voltage so as to make up for the defects of the linear chain or branched chain carboxylic ester, and the circulation performance of the electrolyte is improved.

In order to solve the second technical problem, the invention adopts the technical scheme that:

a method for preparing the electrolyte for the double-ion battery comprises the following steps:

and dispersing lithium salt, fluorine salt and an additive in a solvent, and stirring to obtain the electrolyte for the double-ion battery.

In still another aspect of the present invention, there is also provided a lithium ion battery comprising a positive electrode sheet containing a positive electrode active material, a negative electrode sheet containing a negative electrode active material, a lithium battery separator, and the above electrolyte for a bi-ion battery.

One of the above technical solutions has at least one of the following advantages or beneficial effects:

1. the modified N, N' -carbonyldiimidazole and hexachlorocyclotriphosphazene reduce the viscosity of the electrolyte for the double-ion battery and improve the ionic conductivity of the electrolyte;

2. the linear chain or branched chain carboxylic ester is used as a solvent with low freezing point, low viscosity and high dielectric constant, and is beneficial to reducing the viscosity of the electrolyte for the double-ion battery and improving the high-rate charging performance of the lithium ion battery;

3. the dimethyl sulfonate can inhibit the linear chain or branched chain carboxylic ester from continuously generating oxidation reaction at the anode under high voltage;

4. due to the synergistic effect of the components, the viscosity of the electrolyte is reduced, the viscosity of the electrolyte is lower, and the formation of lithium fluoride from fluorine ions in fluorine salt and lithium ions in lithium salt in the discharging process can be accelerated, so that the double-ion battery is formed. In addition, the side reaction of the electrolyte with low viscosity in the discharging process can be greatly reduced, thereby improving the cycle performance of the battery.

Detailed Description

In order to explain the technical content, the objects and the effects of the present invention in detail, the following description will be given with reference to the embodiments.

Example 1

2.3g of lithium hexafluorophosphate, 1.5g of hexachlorocyclotriphosphazene, 0.6g of modified N, N' -carbonyldiimidazole and 0.1g of dimethyl sulfonate were dispersed in 50mL of CH₃CH₂CH₂And stirring the solution in a COOCHF solvent to obtain the electrolyte for the dual-ion battery, wherein the viscosity of the electrolyte for the dual-ion battery is 0.8-1.50mpa & s.

Example 2

4.6g of lithium hexafluorophosphate, 2.5g of hexachlorocyclotriphosphazene, 1.0g of modified N, N' -carbonyldiimidazole and 0.5g of dimethyl sulfonate were dispersed in 50mL of CH₃CH₂CH₂And stirring in a COOCHF solvent to obtain the electrolyte for the dual-ion battery.

Comparative example 1

2.3g of lithium hexafluorophosphate, 1.5g of hexachlorocyclotriphosphazene, 0.6g of modified N, N' -carbonyldiimidazole and 0.1g of dimethyl sulfonate were dispersed in 50mL of water, and stirred to obtain the electrolyte for a bipolar battery.

Comparative example 2

2.3g of lithium hexafluorophosphate, 0.6g of modified N, N' -carbonyldiimidazole and 0.1g of dimethyl sulfonate were dispersed in 50mL of CH₃CH₂CH₂And stirring in a COOCHF solvent to obtain the electrolyte for the dual-ion battery.

Comparative example 3

2.3g of lithium hexafluorophosphate and 1.5g of hexafluorocyclotriphosphazene were dispersed in 50mL of CH₃CH₂CH₂And stirring in a COOCHF solvent to obtain the electrolyte for the dual-ion battery.

And (3) performance testing:

li₂MnSiO₄The battery comprises a positive electrode, a negative electrode, a PE diaphragm and the electrolyte prepared according to the invention.

The test results of the specific discharge capacity and the viscosity of the experimental examples 1 to 2 and the comparative examples 1 to 3 were as follows:

the viscosity of the electrolyte was measured with the wushure capillary viscosity based on Poiseuille's law: according to Poiseuille's law, the viscosity of a liquid flowing through a capillary viscometer is η ═ a · ρ · t- (B · ρ)/t, where A, B is the instrument constant of the viscometer, ρ is the liquid density, and t is the time for the liquid to flow through two calibration lines on the viscometer.

TABLE 1

	Viscosity (mPa. s)	Specific discharge capacity (mAh/g)
			Example 1	0.8	768.3
Example 2	1.5	718.2
			Comparative example 1	2.6	694.1
Comparative example 2	4.8	618.2
			Comparative example 3	2.5	688.4

The above description is only an example of the present invention and is not intended to limit the scope of the present invention, and all equivalent modifications made by the present invention as described in the specification of the present invention or directly or indirectly applied to the related technical fields are included in the scope of the present invention.