A sulfur-containing electrode, a lithium-sulfur battery containing the electrode, and a preparation method thereof

Abstract

The invention belongs to the field of lithium-sulfur batteries, and in particular relates to a lithium-sulfur battery electrode, including a current collector and a coating layer. The coating layer has an n-layer structure, and 2≤n, and the order from the current collector to the surface layer of the coating is the first 1st layer, 2nd layer, ..., nth layer; the i-th layer of coating (1≤i≤n) includes sulfur-containing active materials, conductive agents, and adhesives, and the conductive agents are grafted with polar functional groups , the mass of the polar functional group is wi% of the mass of the conductive agent, the polarity of the polar functional group is 〥i, and wi%≤wi+1% or / and 〥i≤〥i+ 1. The closer to the current collector, the lower the content of polar functional groups, the better the conductivity of the conductive agent, which is conducive to reducing the resistance of the overall pole piece; the closer to the coating surface, the higher the content of polar functional groups or the greater the polarity, the conductive agent has a greater impact on the polarity. The stronger the adsorption of lithium sulfide, the stronger the ability of the overall electrode to fix lithium sulfide, so the diffusion of lithium sulfide to the negative electrode affects the cycle performance of the battery.

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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