Sulfur-containing electrode, lithium sulfur battery containing same, and preparation method for lithium sulfur battery

Abstract

The invention belongs to the field of a lithium sulfur battery, and in particular relates to a lithium sulfur battery electrode. The lithium sulfur battery electrode comprises a current collector and a coating layer; the coating layer is in an n-layer structure and n is less than or equal to 2; the n-layer structure of the coating layer from the current collector to the surface layer of the coating layer comprises the first layer, the second layer until the n(th) layer; the i(th) layer ( i is greater than or equal to 1 and less than or equal to n) comprises a sulfur-containing active substance, a conductive agent and a binder; the conducive agent is grafted with a polar functional group; the mass of the polar functional group is wi% of the mass of the conductive agent; the polarity magnitude of the polar functional group is delta i, and wi% is less than or equal to wi+1% and / or delta i% is less than or equal to Wui+1%. The content of the polar functional group becomes lower when the polar functional group is closer to the current collector, and the conductivity of the conductive agent becomes better, so that the resistance of the overall pole piece can be reduced; the content of the polar functional group becomes more or the polarity of the polar functional group becomes higher when the polar functional group is closer to the surface of the coating layer, and the absorption of the conductive agent on the lithium sulfide becomes stronger, and the capability of the overall electrode in fixing the lithium sulfide becomes higher, so that the problem that the cycling performance of the battery is affected when the lithium sulfide is diffused to the negative electrode is solved.

Description

technical field [0001] The invention belongs to the field of lithium-sulfur batteries, and in particular relates to a sulfur-containing electrode, a lithium-sulfur battery containing the electrode and a preparation method thereof. Background technique [0002] Since 1991, carbon materials were creatively used in the field of lithium-ion batteries and brought about revolutionary changes in this field, that is, after multiple charging and discharging efficiently and safely, they have been widely used in mobile phones, cameras, and notebooks. computers and other portable appliances. Compared with traditional lead-acid, Ni-Cd, MH-Ni batteries, lithium-ion batteries have higher specific volume energy density, specific gravimetric energy density, better environmental friendliness, smaller self-discharge and longer battery life. It is an ideal power supply for mobile appliances, power supplies for electric vehicles, and storage appliances for power stations in the 21st century. ...

AI Technical Summary

Problems solved by technology

However, elemental sulfur itself is not conductive, and must be combined with a conductive substance to make an electrode. Due to the introduction of a conductive agent as a conductive component, the content of sulfur in the positive electrode coating has been greatly reduced, thereby reducing the lithium sulfur content. The energy density of the battery; at the same time, during the charging and discharging process of the lithium-sulfur battery, the elemental sulfur will be converted into polysulfides, and the polysulfides will be dissolved in the liquid organic electrolyte, resulting in the loss of active materials during the cycle, which is more serious Unfortunately, the dissolved sulfide will precipitate on the negative electrode to form dendrites, which has a great risk of piercing the separator, resulting in extremely poor safety of the battery.

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