A kind of lithium-sulfur battery cathode material and preparation method thereof

Abstract

The invention discloses a lithium-sulfur battery cathode material. The lithium-sulfur battery cathode material comprises a cathode sulfur-containing active substance, wherein the surface of the cathode sulfur-containing active substance is uniformly and controllably coated with one layer of hydrophilic higher molecular weight cladding membrane. According to the lithium-sulfur battery cathode material, the surface of the cathode sulfur-containing active substance is uniformly and controllably coated with the hydrophilic higher molecular weight cladding membrane, so that a shuttle effect of thesulfur-containing active substance in a charging / discharging process is inhibited to the greatest extent; meanwhile, the lithium ion transmission speed of the battery is extremely enhanced in a high-rate charging / discharging process; the surface of the sulfur-containing active substance is uniformly and controllably coated with the hydrophilic higher molecular weight cladding membrane. The sulfur-containing active substance adopts a sulfur-carbon compound with a porous structure and the pore diameter is about 5nm; a sulfur fixing effect is good and a battery diaphragm does not need to ne modified; polysulfide generated in the charging / discharging process of a lithium-sulfur battery is not gathered on the diaphragm and the diaphragm is prevented from being blocked or aggravated battery polarization is avoided, so that the charging / discharging performance of the lithium-sulfur battery is greatly improved and the service life is greatly prolonged.

Description

technical field [0001] The invention belongs to the technical field of electrochemical energy and nanometer material preparation, and in particular relates to a lithium-sulfur battery cathode material and a preparation method thereof. Background technique [0002] Lithium-sulfur batteries have attracted much attention due to their high energy density, but during charging and discharging, the polysulfides produced at the cathode are easily soluble in the electrolyte and diffuse to the anode to react with lithium, forming a lithium sulfide insulating layer that is insoluble in the electrolyte on the lithium surface. Lithium loses its electrochemical activity. At the same time, due to the dissolution of polysulfides in the cathode, the active material on the sulfur electrode is also continuously reduced, resulting in a rapid decline in the capacity of the lithium-sulfur battery. In addition, the diffusion of polysulfides between the positive and negative electrodes may also be...

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Problems solved by technology

[0003] Chinese patent CN 105280867 A provides a special modified separator for lithium-sulfur battery and its preparation method. A layer of Ketjen Black-coated metal oxide modified coating added with a conductive agent is coated on the surface of the ordinary separator near the positive electrode. layer, although it can alleviate the shuttle effect of polysulfides to a certain extent, a large part of the polysulfides generated during the charge and discharge process will accumulate on the separator or cover the separator, thus blocking the separator and increasing the lithium Ion migration resistance, especially when charging and discharging lithium ions at a high rate of current, the resistance of the barrier layer is very large, which makes the electrode polarization of lithium ions particularly serious during charging and discharging, and makes most of the sulfur inactive.

[0004] Chinese patent CN 102208645 B provides a cathode material for a lithium-sulfur battery, including a sulfur-based cathode active material and amorphous carbon. The amorphous carbon is uniformly and densely coated on the surface of the sulfur-based cathode active material. The particle size of the sulfur-based cathode active material is The thickness of the amorphous carbon layer is 1-5nm. The specific capacity of the lithium-sulfur battery using this positive electrode material is about 800mAh. The capacity retention rate after 100 cycles is 68-82%, and the cycle performance is poor.

Therefore, there is room for further improvement in the performance of the existing lithium-sulfur batteries, such as charge-discharge capacity and cycle life.

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