阅读说明：本技术 一种锂硫电池正极材料及其制备方法 (Lithium-sulfur battery positive electrode material and preparation method thereof ) 是由 赵永男 高海燕 王淑霏 于 2019-04-02 设计创作，主要内容包括：本发明公开了一种酞菁铜-硫共聚物的制备方法,将酞菁铜与一定比例的单质硫混合均匀,球磨反应后得到酞菁铜-硫共聚物。本发明方法简便且无需其他试剂。采用本方法制备的酞菁铜-硫共聚物含硫量高,并且组装的电池具有较好的电化学性能。(The invention discloses a preparation method of copper phthalocyanine-sulfur copolymer, which comprises the steps of uniformly mixing copper phthalocyanine and a certain proportion of elemental sulfur, and carrying out ball-milling reaction to obtain the copper phthalocyanine-sulfur copolymer. The method is simple and convenient and does not need other reagents. The copper phthalocyanine-sulfur copolymer prepared by the method has high sulfur content, and the assembled battery has better electrochemical performance.)

1. A preparation method of a positive active material copper phthalocyanine-sulfur copolymer of a lithium sulfur battery is characterized in that after elemental sulfur and copper phthalocyanine with different proportions are uniformly mixed, a compound and a grinding ball are put into a ball milling tube according to the proportion. Removing air in the tube, and putting the tube into a micro-vibration ball mill for ball milling for a certain time to obtain the copper phthalocyanine-sulfur copolymer.

2. The method of claim 1, wherein the elemental sulfur is 45-90 wt% of the copper phthalocyanine-sulfur copolymer.

3. The method of claim 1, wherein the pellet-to-feed ratio is 4: 1 to 1: 1.

4. The method for preparing the phthalocyanine copper-sulfur copolymer as the positive electrode active material of the lithium-sulfur battery as recited in claim 1, wherein the rotation speed of the ball mill is 500 to 4000r/min, and the ball milling time is 0.5 to 4 hours.

5. The method according to claim 1, wherein the ball-milling tube is made of polytetrafluoroethylene, and the grinding ball is a zirconia grinding ball with a diameter of 0.5 mm.

Technical Field

The invention provides a positive electrode material for a lithium-sulfur battery and a preparation method thereof.

Background

With the increasing reliance on portable power sources, efficient and economical energy storage technologies play an important role in green and sustainable energy demand. The theoretical specific capacity of the lithium-sulfur battery is up to 1675mAh/g, and the lithium-sulfur battery is one of the most promising energy storage devices. It suffers from a number of problems in the commercial development: the positive active substance has low sulfur utilization rate and poor conductivity, and the intermediate product has the dissolution shuttle effect and the volume expansion in the electrochemical reaction process. How to improve the conductivity of the positive electrode material and to suppress the dissolution of lithium polysulfide in the electrolyte has been the focus of research. In recent years, porous carbon materials have become popular sulfur carriers due to their good electrical conductivity and abundant pore structure. The porous structure has the function of absorbing the pore passages of lithium polysulfide, and the dissolution of the lithium polysulfide is inhibited to a certain extent. Researchers have doped N, P and some transition metal elements, etc. into carbon materials, and it is expected that these polar atoms will enhance the ability of the material to adsorb lithium polysulfides. Recently, sulfur-containing polymers have also attracted a wide range of attention. The sulfur molecules are connected with the organic molecules in a covalent bond mode, so that the active substance sulfur and the carrier material always have chemical bond action in the electrochemical reaction process, the dissolution of lithium polysulfide in electrolyte can be effectively inhibited, and the battery capacity is improved.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a copper phthalocyanine-sulfur copolymer and a preparation method thereof, wherein the copper phthalocyanine and elemental sulfur are prepared by simple mechanical ball milling. The preparation method is simple and easy to operate, and the obtained copper phthalocyanine-sulfur copolymer can effectively inhibit the dissolution of lithium polysulfide and improve the electrochemical performance of the lithium sulfur battery.

The purpose of the invention is realized by the following technical scheme:

a phthalocyanine copper-sulfur copolymer as the positive electrode of Li-S battery is prepared from elementary sulfur and copper phthalocyanine through copolymerizing by simple mechanical ball grinding method. The reaction is carried out under the action of mechanical force to form C-S bond.

The invention is realized by the following steps:

uniformly mixing copper phthalocyanine powder and elemental sulfur in different proportions, wherein the mass percentage of the elemental sulfur is 45-90%, putting the compound and a grinding ball into a ball milling tube according to the mass ratio of 1: 3, removing air in the tube, and putting the tube into a micro-vibration ball mill for ball milling. The rotating speed is 3000r/min, and the ball milling time is 1 h.

Compared with other preparation methods, the preparation method of the phthalocyanine copper-sulfur copolymer as the positive electrode active material of the lithium-sulfur battery provided by the invention has the advantages that the required materials are cheap and easy to obtain, the equipment is simple, the operation is convenient, the economy and the safety are realized, and the prepared materials have high specific discharge capacity. This is because the conjugated structure in copper phthalocyanine makes it have good conductivity, and polar atoms such as N, Cu in copper phthalocyanine have a certain adsorption effect on lithium polysulfide, and after it is ball-milled and reacted with elemental sulfur, C in phthalocyanine molecules is covalently bonded with activated S under the action of mechanical force, so that polysulfide generated in the electrochemical reaction process is bound by copolymer molecules in the form of covalent bonds. Inhibiting the dissolution of polysulfides and relieving volume expansion, thereby improving the electrochemical performance thereof.

Drawings

Fig. 1 is a charge-discharge cycle curve at 0.1C for a battery assembled with pure elemental sulfur as the positive electrode active material.

FIG. 2 is a charge-discharge cycle curve at 0.5C for a battery assembled with the copper phthalocyanine-sulfur copolymer of the present invention as a positive electrode active material;

FIG. 3 is a graph of rate performance of a battery assembled with a copper phthalocyanine-sulfur copolymer of the present invention as a positive active material;

FIG. 4 is a Raman (Raman) spectrum of a copper phthalocyanine-sulfur copolymer of the present invention and copper phthalocyanine.

Detailed Description

A preparation method of a positive active material copper phthalocyanine-sulfur copolymer of a lithium-sulfur battery comprises the following steps: