Preparation method of cathode of the lithium-sulfur battery

Abstract

The present invention provides a preparation method of a cathode of a lithium-sulfur battery. The method comprises the steps of: dispersing sulfur on the surface of a conductive agent to prepare a sulfur-conductive agent compound; mixing the sulfur-conductive agent compound with conductive carbon black and a binder to prepare a sulfur electrode; and preparing a layer of Ti4O7 film on the surface of the sulfur electrode through adoption of a coating deposition method to prepare a conductive layer-sulfur positive electrode. The method comprises the following steps of: (1) preparing a sulfur-conductive agent compound; (2) preparing a sulfur electrode; and (3) preparing a conductive layer-sulfur electrode. According to the method, sulfur is uniformly dispersed on the surface of the conductiveagent, the contact area of sulfur and the conductive agent is increased, and the conductivity of sulfur is improved. After the sulfur electrode is prepared, a conductive Ti4O7 layer is prepared on thesurface of the sulfur electrode through adoption of a coating deposition method, and the Ti4O7 layer is used for preventing an intermediate product lithium polysulfide from being dissolved in an electrolyte, so that the loss amount of active substances is reduced, the structure of the sulfur electrode is stabilized, and the specific discharge capacity and the cyclic discharge stability of the sulfur electrode are improved.

Description

technical field [0001] The invention relates to a method for preparing a positive electrode of a lithium-sulfur battery, belonging to the technical field of lithium batteries. Background technique [0002] The lightening of mobile electronic devices and the development of electric vehicles require batteries to have higher energy density, and the use of high specific capacity electrode materials is an effective way to increase the energy density of batteries. Lithium battery has high energy density. Lithium-sulfur battery is a secondary lithium battery, which uses sulfur as the positive electrode reaction substance. The theoretical mass specific capacity of sulfur is 1675mAhg -1 , the theoretical energy density is 2600Whkg -1 . In addition, sulfur is cheap and environmentally friendly, which makes lithium-sulfur batteries promising. [0003] Lithium-sulfur batteries have some problems: [0004] Compared with the theoretical discharge specific capacity of sulfur, the actua...

AI Technical Summary

Problems solved by technology

The problem of lithium-sulfur batteries is caused by the internal reaction of the battery. First, the conductivity of sulfur at 25°C is 5×10-30Scm-1, and sulfur is an electronic insulator. , the sulfur that is not in contact with the conductive agent cannot undergo electrochemical reactions, which results in the actual discharge specific capacity of the battery being low

Secondly, when lithium ions react with sulfur molecules, an intermediate product lithium polysulfide will be generated. Lithium polysulfide is easily dissolved in organic ether electrolytes, and the dissolution of lithium polysulfide will cause the loss of electrode active materials.

Again, in the initial sulfur electrode, the distribution of sulfur is evenly dispersed. During the discharge process, lithium polysulfide dissolved in the electrolyte reacts with lithium ions to form lithium disulfide and lithium sulfide, which are insoluble in the electrolytic solution. They are deposited on the surface of the sulfur electrode. During the cycle charge and discharge process, the active material in the sulfur electrode is continuously dissolved and deposited, resulting in the aggregation of the active material, which reduces the reactivity of the active material and makes the discharge capacity of the battery continuously decrease.

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