阅读说明：本技术 一种硫电极的制备方法 (Preparation method of sulfur electrode ) 是由 李仕琦 冷丹 汶飞 邓天松 李丽丽 于 2021-06-28 设计创作，主要内容包括：本发明公开了一种硫电极的制备方法,主要采用光照硫脲使得硫脲分解的方式制备硫电极。采用本发明的技术方案,可以很好地将硫脲与宿主材料混合,最终得到单质硫与宿主材料均匀混合的硫电极,从而阻止正极聚硫锂向负极扩散,抑制锂硫电池的穿梭效应,提高锂硫电池的库伦效率,提升锂硫电池的循环稳定性。(The invention discloses a preparation method of a sulfur electrode, which mainly adopts a mode of irradiating thiourea to decompose the thiourea to prepare the sulfur electrode. By adopting the technical scheme of the invention, thiourea can be well mixed with the host material, and the sulfur electrode with the uniformly mixed elemental sulfur and the host material is finally obtained, so that the diffusion of the positive polysulfide lithium to the negative electrode is prevented, the shuttle effect of the lithium-sulfur battery is inhibited, the coulombic efficiency of the lithium-sulfur battery is improved, and the cycle stability of the lithium-sulfur battery is improved.)

1. A method for preparing a sulfur electrode, comprising the steps of:

step S1, dissolving thiourea in deionized water to obtain a thiourea aqueous solution;

step S2, uniformly mixing the carbon material and the thiourea aqueous solution;

and step S3, irradiating the aqueous solution of thiourea to decompose the thiourea to obtain the sulfur electrode.

2. The method of manufacturing a sulfur electrode according to claim 1, wherein the concentration of thiourea is 10mol/L in step S1.

3. The method of manufacturing a sulfur electrode according to claim 1, wherein the mass ratio of the carbon material to thiourea is 1:8 in step S2.

4. The method of claim 1, wherein the light source used in step S3 has a wavelength of 375 nm.

Technical Field

The invention belongs to the technical field of lithium-sulfur batteries, and particularly relates to a preparation method of a sulfur electrode.

Background

In order to effectively utilize renewable energy, we need to store it. Therefore, charging and discharging the battery will function sufficiently in this field. The lithium-sulfur battery has extremely high theoretical specific capacity (1675mAh/g) and theoretical specific energy (2600Wh/kg), and the elemental sulfur has the characteristics of environmental friendliness, abundant raw materials, low cost and the like, so the lithium-sulfur battery is considered as a next-generation charge and discharge battery.

However, problems still face to realize commercialization of lithium-sulfur batteries, among which lithium polysulfides (Li)₂S_xAnd x is more than or equal to 4 and less than or equal to 8) is a main reason for reducing the coulombic efficiency of the battery and the cycle life of the lithium-sulfur battery. In recent years, researchers have made many studies on how to eliminate the shuttling effect of lithium sulfur batteries to improve the cycle performance of the batteries. In order to prevent the polysulfide lithium from diffusing in the organic electrolyte, one of the most effective methods is to mix elemental sulfur with carbon materials, such as carbon materials of carbon nanotubes, mesoporous carbon, carbon spheres, etc., and compound or coat the carbon materials with sulfur, but the shuttle effect is not effectively solved. By adopting the method, the elemental sulfur cannot be uniformly mixed with the carbon material, so that the utilization rate of the elemental sulfur is low, the coulombic efficiency of the lithium-sulfur battery is low, and the cycle stability is poor. Therefore, a more efficient method for preparing sulfur electrodes is also sought.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides a preparation method of a sulfur electrode, which mainly adopts a mode of irradiating thiourea to decompose thiourea to prepare the sulfur electrode. By adopting the technical scheme of the invention, thiourea can be well mixed with the host material, and the sulfur electrode with the uniformly mixed elemental sulfur and the host material is finally obtained, so that the diffusion of the positive polysulfide lithium to the negative electrode is prevented, the shuttle effect of the lithium-sulfur battery is inhibited, the coulombic efficiency of the lithium-sulfur battery is improved, and the cycle stability of the lithium-sulfur battery is improved.

In order to solve the problems in the prior art, the invention provides a novel method for preparing a sulfur electrode, which comprises the following steps:

step S1, dissolving thiourea in deionized water to obtain a thiourea aqueous solution;

step S2, uniformly mixing the carbon material and the thiourea aqueous solution;

and step S3, irradiating the aqueous solution of thiourea to decompose the thiourea to obtain the sulfur electrode.

Preferably, in step S1, the concentration of thiourea is 10 mol/L.

Preferably, in step S2, the mass ratio of the carbon material to thiourea is 1: 8.

Preferably, in step S3, the wavelength of the light source used is 375 nm.

Compared with the prior art, the invention has the following beneficial effects:

(1) the method provided by the invention is simple in process and easy to realize.

(2) Thiourea and a carbon material are effectively and uniformly mixed, and the sulfur electrode material with elemental sulfur uniformly dispersed in the carbon material is obtained after illumination.

(3) The coulombic efficiency of the lithium-sulfur battery is improved, and the cycling stability of the battery is enhanced.

Drawings

Fig. 1 is a cycle capacity curve of a lithium sulfur battery of example 1 of the present invention at a charge and discharge current of 0.2C; wherein, (a) the cyclic capacity curve of the resulting sulfur electrode of inventive instantiation 1 at a charge-discharge current of 0.2C; (b) the circulating capacity curve of the sulfur electrode prepared by the traditional method under the charge-discharge current of 0.2C is shown.

The following specific embodiments will further illustrate the invention in conjunction with the above-described figures.

Detailed Description

In order to better explain the process and scheme of the present invention, the following invention is further described with reference to the accompanying drawings and examples. The specific embodiments described herein are merely illustrative of the invention and do not delimit the invention.

The invention provides a preparation method of a novel sulfur electrode, which comprises the following steps:

step S1, dissolving thiourea in deionized water to obtain a thiourea aqueous solution;

step S2, uniformly mixing the carbon material and the thiourea aqueous solution;

and step S3, irradiating the aqueous solution of thiourea to decompose the thiourea to obtain the sulfur electrode.

According to the technical scheme, the carbon material and the thiourea are uniformly mixed, and the thiourea is decomposed through illumination to obtain the sulfur electrode in which elemental sulfur is uniformly dispersed in the carbon material, so that the electronic conductivity of the sulfur electrode is improved, the shuttle effect of the polysulfide lithium is inhibited, and the cycle stability of the lithium-sulfur battery is improved.

EXAMPLE 1

Dissolving thiourea in deionized water to obtain 10M/L thiourea aqueous solution; mixing porous carbon with thiourea aqueous solution, wherein the mass ratio of the carbon material to the thiourea is 1: 8; and irradiating the mixture of the carbon material and thiourea by using light with the wavelength of 375nm to obtain the sulfur-carbon composite material.

Instantiation 2

Dissolving thiourea in deionized water to obtain 10M/L thiourea aqueous solution; mixing porous carbon with thiourea aqueous solution, wherein the mass ratio of the carbon material to the thiourea is 1: 8; and irradiating the mixture of the carbon material and thiourea by using light with the wavelength of 420nm to obtain the sulfur-carbon composite material.

Instantiation 3

Dissolving thiourea in deionized water to obtain thiourea aqueous solution with the concentration of 5M/L; mixing porous carbon with thiourea aqueous solution, wherein the mass ratio of the carbon material to the thiourea is 1: 8; and irradiating the mixture of the carbon material and thiourea by using light with the wavelength of 375nm to obtain the sulfur-carbon composite material.

Instantiation 4

Dissolving thiourea in deionized water to obtain 10M/L thiourea aqueous solution; mixing porous carbon with thiourea aqueous solution, wherein the mass ratio of the carbon material to the thiourea is 1: 4; and irradiating the mixture of the carbon material and thiourea by using light with the wavelength of 375nm to obtain the sulfur-carbon composite material.

Fig. 1(a) is a cyclic capacity curve of the sulfur electrode obtained in the embodiment 1 of the present invention at a charge and discharge current of 0.2C, the specific capacity of the sulfur electrode can reach 550mAh/g, and the attenuation rate per 100 cycles is only 0.001%. Fig. 1(b) shows the electrochemical performance of a sulfur electrode prepared by a conventional method. The electrochemical performance of the sulfur electrodes obtained in examples 2 to 4 was similar to that of example 1.

Further, the performance test is carried out on the method. The specific test process is as follows: the negative electrode of the selected lithium-sulfur battery is a lithium sheet, Celgard2325 is used as a diaphragm, 1mLiTFSI is dissolved in 1, 3-Dioxolane (DOL) and ethylene glycol dimethyl ether (DME) (volume ratio is 1:1) to be used as electrolyte, and the battery is assembled by using an LIR2032 coin-shaped battery case in a glove box which is filled with argon gas for protection and has the humidity and oxygen concentration lower than 1 ppm. In the charge and discharge test system, the charge and discharge test voltage is 1.7V-2.8V.

The analysis can show that the elemental sulfur of the sulfur electrode prepared by the method can be uniformly dispersed in the electrode, so that the electronic conductivity of the electrode is effectively improved, the shuttle effect of the lithium-sulfur battery is inhibited, the specific capacity of the obtained sulfur electrode can reach 550mAh/g under the charge-discharge current of 0.2C, and the attenuation rate of each cycle of 100 times is only 0.001%. The method effectively improves the cycling stability of the battery.

The above description of the embodiments is only intended to facilitate the understanding of the method of the invention and its core idea. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.