CN112928331A

CN112928331A - Electrolyte for lithium-sulfur battery

Info

Publication number: CN112928331A
Application number: CN202110193868.8A
Authority: CN
Inventors: 邓丁榕; 樊晓红; 翁建春; 吴启辉
Original assignee: Jimei University
Current assignee: Jimei University
Priority date: 2021-02-20
Filing date: 2021-02-20
Publication date: 2021-06-08
Anticipated expiration: 2041-02-20
Also published as: CN112928331B

Abstract

The invention relates to an electrolyte for a lithium-sulfur battery, which comprises a basic component and an additive, wherein the additive comprises one or more of ruthenium terpyridine chloride, cobalt terpyridine chloride, nickel terpyridine chloride and ferric terpyridine chloride. The invention can optimize the reaction electromechanics of the battery, improve the reaction rate, reduce the resistance between the electrode and the electrolyte, and improve the capacity, cycle life and rate capability of the battery. The terpyridine group can be effectively adsorbed on a conductive agent and a carbon material, so that the conductive capacity of the whole electrode is improved, the metal element and the chlorine element can effectively adsorb polysulfide and catalyze the conversion reaction of sulfur, the capacity of the battery is improved, and the shuttle effect of the battery is reduced.

Description

Electrolyte for lithium-sulfur battery

Technical Field

The present invention relates to an electrolyte for a lithium-sulfur battery.

Background

With the development of economy and science and technology, the energy structure of human beings is continuously changing towards a clean and sustainable direction. At present, lithium ion batteries with high energy density and long cycle life have become the main power source of consumer electronics products, playing an important role. However, with the development of high specific energy mobile devices, lithium ion batteries have been difficult to meet the current market demand. Phase (C)Compared with the traditional lithium ion battery, the lithium-sulfur battery has the advantages of ultrahigh theoretical specific capacity (1675mAh/g), theoretical energy density (2600Wh/kg), rich sulfur storage capacity, low price and the like, so the lithium-sulfur battery is considered to be one of novel energy storage systems with development potential, and can be applied to the fields of portable electronic products, power automobiles, large-scale energy storage and the like. However, lithium sulfur batteries still have many problems and challenges, such as elemental S reactant for the battery system₈And the final reduction product Li₂S₂And Li₂S has extremely low electronic and ionic conductivity, volume change of electrodes in the charging and discharging processes, and simple substance S₈Polysulfide which can be dissolved in electrolyte is generated in the process of charging and discharging of the battery, the polysulfide is easy to shuttle to the negative electrode of the battery and deposits on the surface of metal lithium to cause the defects of irreversible loss of active materials of the battery and the like, and finally, the utilization rate of active materials of the lithium-sulfur battery is low, and the cycling stability of the battery is poor, thereby restricting the development and the application of the lithium-sulfur battery.

Various materials are added into the positive electrode of the lithium-sulfur battery as sulfur framework materials to improve the battery performance. For example, the addition of the carbon material can effectively improve the conductivity of the electrode, and the addition of the oxide material can effectively adsorb polysulfide so as to inhibit the generation of shuttle effect. The addition of a nanoporous material may also provide more room for the volume expansion of sulfur. However, in these methods, a solid-phase material is added to the positive electrode, and the proportion of the active material in the positive electrode tends to be reduced.

Accordingly, the present inventors have made extensive studies to solve the above problems and have made the present invention.

Disclosure of Invention

The invention aims to provide an electrolyte for a lithium-sulfur battery, which can reduce polarization of the lithium-sulfur battery and improve charge-discharge capacity and cycle performance of the lithium-sulfur battery.

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

an electrolyte for a lithium-sulfur battery, the electrolyte comprising a base component and an additive, the additive comprising ruthenium (C) terpyridyl chloride₃₀ H₂₄ Cl₂ N₆Ru), IIIBipyridyl cobalt chloride (C)₃₀ H₂₄ Cl₂ N₆Co), nickel terpyridyl chloride (C)₃₀H₂₄ Cl₂ N₆Ni) and iron (C) terpyridyl chloride₃₀ H₂₄ Cl₂ N₆Fe).

In a preferred embodiment of the present invention, the additive is 0.1 to 5% by mass of the electrolyte.

As a preferable mode of the present invention, the base component includes a nonaqueous organic solvent and a lithium salt, and the mass percentage of the nonaqueous organic solvent in the electrolyte is 80% to 95%.

In a preferred embodiment of the present invention, the lithium salt is one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, lithium bistrifluoromethanesulfonimide, and lithium nitrate.

In a preferred embodiment of the present invention, the concentration of the lithium salt is 0.1mol/L to 1.0 mol/L.

In a preferred embodiment of the present invention, the non-aqueous organic solvent is one or more of a linear ether solvent and a cyclic ether solvent.

In a preferred embodiment of the present invention, the linear ether solvent is ethylene glycol dimethyl ether, diethylene glycol dimethyl ether or a derivative thereof, and the cyclic ether solvent is 1, 3-dioxolane or a derivative thereof.

In a preferred mode of the invention, the non-aqueous organic solvent is prepared by mixing with calcium hydride under an argon glove box, stirring for removing water for one week, and then performing reduced pressure distillation and purification under the protection of nitrogen or inert gas.

After the scheme is adopted, the invention has the beneficial effects that:

one or more of ruthenium terpyridyl chloride, cobalt terpyridyl chloride, nickel terpyridyl chloride and ferric terpyridyl chloride are used as additives of the electrolyte, so that the electrolyte can participate in the charging and discharging process of the lithium-sulfur battery, but does not participate in the battery reaction, and can play a role in changing the dynamics of the electrode process of the battery. The invention can optimize the reaction electromechanics of the battery, improve the reaction rate, reduce the resistance between the electrode and the electrolyte, and improve the capacity, cycle life and rate capability of the battery. The terpyridine group can be effectively adsorbed on a conductive agent and a carbon material, so that the conductive capacity of the whole electrode is improved, the metal element and the chlorine element can effectively adsorb polysulfide and catalyze the conversion reaction of sulfur, the capacity of the battery is improved, and the shuttle effect of the battery is reduced.

And secondly, the additive of the electrolyte has good stability and a simple structure, can be well contacted with a discharge product, and reduces the polarization of the battery.

And thirdly, the electrolyte has simple formula and easy preparation, and is beneficial to mass production.

Drawings

Fig. 1 is a charge-discharge curve diagram of a lithium-sulfur battery produced from the electrolyte of example 1.

Fig. 2 is a graph of cycle performance of a lithium sulfur battery fabricated with the electrolyte of example 1.

Fig. 3 is a graph of rate performance of a lithium sulfur battery fabricated with the electrolyte of example 1.

Detailed Description

In order to further explain the technical solution of the present invention, the following detailed description is made with reference to the embodiments.

The lithium-sulfur battery of the invention refers to a battery using lithium as a negative electrode and sulfur or a sulfur compound as a positive electrode.

Example 1

Mixing linear ether solvent (ethylene glycol dimethyl ether) and cyclic ether solvent (1, 3-dioxolane) in a ratio of 1:1, and removing water. Weighing and dissolving conductive lithium salt lithium trifluoromethanesulfonate and lithium nitrate in the solvent according to the proportion of 0.5mol/L respectively under the atmosphere of helium at room temperature, and uniformly stirring to obtain the basic electrolyte. And adding terpyridyl ruthenium chloride into the basic electrolyte, wherein the mass percentage of the terpyridyl ruthenium chloride in the whole electrolyte is 0.1%, so as to obtain the target electrolyte. The lithium sulfur battery was assembled under a helium atmosphere and a battery test was performed. The blank test object was a cell assembled without the base electrolyte added with ruthenium terpyridine chloride. Both properties are shown with reference to fig. 1-3.

Example 2

Mixing linear ether solvent (ethylene glycol dimethyl ether) and cyclic ether solvent (1, 3-dioxolane) in a ratio of 1:5, and removing water. And weighing the conductive lithium salt lithium bistrifluoromethanesulfonimide and the lithium nitrate according to the proportion of 0.3mol/L respectively under the atmosphere of helium at room temperature, dissolving in the solvent, and uniformly stirring to obtain the basic electrolyte. Ruthenium terpyridyl chloride and cobalt terpyridyl chloride are added into the basic electrolyte, and the mass percentage (relative to the whole electrolyte) of the ruthenium terpyridyl chloride and the cobalt terpyridyl chloride is 0.05% and 0.05%, respectively, so that the target electrolyte is obtained. The lithium sulfur battery was assembled under a helium atmosphere and a battery test was performed. The blank test object was a battery assembled with the base electrolyte without additives.

Example 3

Mixing linear ether solvent (ethylene glycol dimethyl ether) and cyclic ether solvent (1, 3-dioxolane) in a ratio of 3:1, and removing water. Weighing and dissolving conductive lithium salt lithium trifluoromethanesulfonate and lithium hexafluorophosphate in the ratio of 0.3mol/L and 0.7mol/L in the solvent respectively under the atmosphere of helium at room temperature, and stirring uniformly to obtain the basic electrolyte. And adding nickel terpyridyl chloride into the basic electrolyte, wherein the mass percentage (relative to the whole electrolyte) is 0.2%, and thus obtaining the target electrolyte. The lithium sulfur battery was assembled under a helium atmosphere and a battery test was performed. The blank test object was a battery assembled without the base electrolyte added with nickel terpyridine chloride.

In the invention, the additive adopts one or more of ruthenium terpyridine chloride, cobalt terpyridine chloride, nickel terpyridine chloride and ferric terpyridine chloride, and the effect similar to that of the embodiment 1 can be achieved.

The product form of the present invention is not limited to the embodiments, and any suitable changes or modifications of the similar ideas by anyone should be considered as not departing from the patent scope of the present invention.

Claims

1. An electrolyte for a lithium-sulfur battery, the electrolyte comprising a base component and an additive, characterized in that: the additive comprises one or more of ruthenium terpyridine chloride, cobalt terpyridine chloride, nickel terpyridine chloride and ferric terpyridine chloride.

2. The electrolyte for a lithium-sulfur battery according to claim 1, wherein: the mass percentage of the additive in the electrolyte is 0.1-5%.

3. The electrolyte for a lithium-sulfur battery according to claim 2, wherein: the basic components comprise a nonaqueous organic solvent and lithium salt, wherein the mass percentage of the nonaqueous organic solvent in the electrolyte is 80-95%.

4. The electrolyte for a lithium-sulfur battery according to claim 3, wherein: the lithium salt is one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, lithium bistrifluoromethanesulfonimide and lithium nitrate.

5. The electrolyte for a lithium-sulfur battery according to claim 4, wherein: the concentration of the lithium salt is 0.1mol/L-1.0 mol/L.

6. The electrolyte for a lithium-sulfur battery according to claim 5, wherein: the non-aqueous organic solvent is one or more of linear ether solvents or annular ether solvents.

7. The electrolyte for a lithium-sulfur battery according to claim 6, wherein: the linear ether solvent is ethylene glycol dimethyl ether, diethylene glycol dimethyl ether or derivatives thereof, and the annular ether solvent is 1, 3-dioxolane or derivatives thereof.

8. The electrolyte for a lithium-sulfur battery according to claim 7, wherein: the non-aqueous organic solvent is prepared by mixing with calcium hydride under an argon glove box, stirring for removing water for one week, and then carrying out reduced pressure distillation and purification under the protection of nitrogen or inert gas.

9. The electrolyte for a lithium-sulfur battery according to any one of claims 1 to 7, wherein: lithium sulfur batteries use lithium as the negative electrode and sulfur or sulfur complexes as the positive electrode.