CN112928331B - Electrolyte for lithium-sulfur battery - Google Patents

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

A kind of electrolyte for lithium-sulfur battery

technical field

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

Background technique

With the development of economy and science and technology, the energy structure of human beings is constantly 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 electronic products and play 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. Compared with traditional lithium-ion batteries, lithium-sulfur batteries are considered to be the most popular due to their ultra-high theoretical specific capacity (1675mAh/g), theoretical energy density (2600Wh/kg), abundant sulfur reserves and low price. It is one of the new energy storage systems with development potential, which can be applied to the fields of portable electronic products, power vehicles and large-scale energy storage. However, there are still many problems and challenges in lithium-sulfur batteries. For example, the reactant element S ₈ of the battery system and the final reduction products Li ₂ S ₂ and Li ₂ S have extremely low electronic and ionic conductivities. Volume change, and elemental S ₈ produce polysulfides soluble in the electrolyte during the charging and discharging process of the battery, which are easy to shuttle to the negative electrode of the battery and deposit on the surface of metal lithium, causing irreversible loss of battery active materials and other defects, which will eventually lead to lithium Sulfur batteries suffer from low utilization of active materials and poor cycle stability, which restrict the development and application of lithium-sulfur batteries.

Various materials are added to the cathode of lithium-sulfur batteries as sulfur framework materials to improve battery performance. For example, the addition of carbon materials can effectively improve the conductivity of the electrode, and the addition of oxide materials can effectively adsorb polysulfides to inhibit the generation of the shuttle effect. In addition, the addition of nanoporous materials can also provide more space for the volume expansion of sulfur. However, these methods all add solid-phase materials to the positive electrode, which will inevitably reduce the proportion of active materials in the positive electrode.

In view of this, the inventor of this case has conducted in-depth research on the above-mentioned problems, and this case came into being.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide an electrolyte for a lithium-sulfur battery that can reduce the polarization of the lithium-sulfur battery and improve its charge-discharge capacity and cycle performance.

In order to achieve the above object, the present invention adopts such technical scheme:

An electrolyte for a lithium-sulfur battery, the electrolyte includes basic components and additives, the additives include ruthenium terpyridine chloride (C ₃₀ H ₂₄ Cl ₂ N ₆ Ru), cobalt terpyridine chloride (C ₃₀ H ₂₄ Cl ) ₂ N ₆ Co), one or more of terpyridine nickel chloride (C ₃₀ H ₂₄ Cl ₂ N ₆ Ni) and terpyridine ferric chloride (C ₃₀ H ₂₄ Cl ₂ N ₆ Fe).

As a preferred mode of the present invention, the mass percentage of the additive in the electrolyte is 0.1%-5%.

As a preferred mode of the present invention, the basic components include a non-aqueous organic solvent and a lithium salt, and the mass percentage of the non-aqueous organic solvent in the electrolyte is 80%-95%.

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

As a preferred mode of the present invention, the concentration of the lithium salt is 0.1 mol/L-1.0 mol/L.

As a preferred mode of the present invention, the non-aqueous organic solvent is one or more of linear ether solvents or cyclic ether solvents.

As a preferred mode of the present invention, the linear ether solvent is ethylene glycol dimethyl ether, diethylene glycol dimethyl ether or derivatives thereof, and the cyclic ether solvent is 1,3-dioxane or its derivatives.

As a preferred mode of the present invention, the non-aqueous organic solvent is prepared by mixing with calcium hydride to remove water for a week under an argon glove box, and then purifying under reduced pressure under the protection of nitrogen or inert gas.

After adopting the above scheme, the beneficial effects that the present invention has are:

1. The present invention can participate in the charging and discharging of lithium-sulfur batteries due to the adoption of one or more of terpyridine ruthenium chloride, terpyridine cobalt chloride, terpyridine nickel chloride and terpyridine ferric chloride as additives for the electrolyte. The process does not participate in the battery reaction itself, and can play a role in changing the kinetics of the battery electrode process. The invention can optimize the battery reaction electricity, improve the reaction rate, reduce the resistance between the electrode and the electrolyte, and improve the capacity, cycle life and rate performance of the battery. Among them, the terpyridine group can be effectively adsorbed on the conductive agent and carbon material to improve the conductivity of the overall electrode, while the metal element and chlorine element can effectively adsorb polysulfide and catalyze the conversion reaction of sulfur, improve the battery capacity and Reduce the shuttle effect of the battery.

Second, the additive of the electrolyte has good stability, simple structure, good contact with the discharge product, and reduces the polarization of the battery.

3. The electrolyte has a simple formula, is easy to prepare, and is beneficial to mass production.

Description of drawings

FIG. 1 is a charge-discharge curve diagram of a lithium-sulfur battery fabricated with the electrolyte solution of Example 1. FIG.

FIG. 2 is a cycle performance diagram of the lithium-sulfur battery fabricated with the electrolyte of Example 1. FIG.

FIG. 3 is a graph of the rate performance of the lithium-sulfur battery fabricated with the electrolyte of Example 1. FIG.

Detailed ways

In order to further explain the technical solutions of the present invention, detailed descriptions are given below with reference to the embodiments.

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

Example 1

A linear ether solvent (ethylene glycol dimethyl ether) was mixed with a cyclic ether solvent (1,3-dioxane) in a ratio of 1:1, and the water was removed. Under a helium atmosphere at room temperature, the conductive lithium salts lithium trifluoromethanesulfonate and lithium nitrate are respectively weighed in a ratio of 0.5 mol/L and dissolved in the above solvent, and stirred evenly to obtain a basic electrolyte. The ruthenium terpyridine chloride is added to the above-mentioned basic electrolyte, and the mass percentage of the ruthenium terpyridine chloride in the whole electrolyte is 0.1% to obtain the target electrolyte. Lithium-sulfur batteries were assembled and tested under helium atmosphere. The blank test object is the battery assembled with the base electrolyte without the addition of ruthenium terpyridine chloride. The performance of the two is shown in Figure 1-3.

Example 2

A linear ether solvent (ethylene glycol dimethyl ether) was mixed with a cyclic ether solvent (1,3-dioxane) in a ratio of 1:5, and the water was removed. Under a helium atmosphere at room temperature, the conductive lithium salt lithium bis-trifluoromethanesulfonimide and lithium nitrate are respectively weighed in a ratio of 0.3 mol/L, dissolved in the above solvent, and stirred evenly to obtain a basic electrolyte. The ruthenium terpyridine chloride and the cobalt terpyridine chloride are added to the above basic electrolyte, and the mass percentages (relative to the entire electrolyte) are 0.05% and 0.05%, respectively, to obtain the target electrolyte. Lithium-sulfur batteries were assembled and tested under helium atmosphere. The blank test object is the battery assembled with the base electrolyte without added additives.

Example 3

A linear ether solvent (ethylene glycol dimethyl ether) was mixed with a cyclic ether solvent (1,3-dioxane) in a ratio of 3:1, and the water was removed. Under the helium atmosphere at room temperature, the conductive lithium salts lithium trifluoromethanesulfonate and lithium hexafluorophosphate are respectively weighed in proportions of 0.3 mol/L and 0.7 mol/L, dissolved in the above solvent, and stirred evenly to obtain a basic electrolyte. Nickel terpyridine chloride was added to the above-mentioned basic electrolyte, and the mass percentage (relative to the whole electrolyte) was 0.2% to obtain the target electrolyte. Lithium-sulfur batteries were assembled and tested under helium atmosphere. The blank test object is the battery assembled with the base electrolyte without the addition of nickel terpyridine chloride.

In the present invention, the additive adopts one or more of ruthenium terpyridine chloride, cobalt terpyridine chloride, nickel terpyridine chloride and ferric terpyridine chloride, all of which can play an effect similar to Embodiment 1.

The product form of the present invention is not limited to the embodiment of the present case, and anyone who makes appropriate changes or modifications to it in a similar way should be regarded as not departing from the patent scope of the present invention.

Claims (7)

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, the basic components comprise a non-aqueous organic solvent and lithium salt, the mass percentage of the non-aqueous organic solvent in the electrolyte is 80-95%, and the non-aqueous organic solvent is one or more of linear ether solvents or annular ether solvents.

2. The electrolyte for a lithium-sulfur battery as defined in 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 lithium salt is one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, lithium bistrifluoromethanesulfonimide and lithium nitrate.

4. The electrolyte for a lithium-sulfur battery according to claim 3, wherein: the concentration of the lithium salt is 0.1mol/L-1.0 mol/L.

5. The electrolyte for a lithium-sulfur battery according to claim 4, 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.

6. The electrolyte for a lithium-sulfur battery according to claim 5, 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.

7. The electrolyte for a lithium-sulfur battery according to any one of claims 1 to 5, wherein: lithium sulfur batteries use lithium as the negative electrode and sulfur or sulfur complexes as the positive electrode.

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