A graphene electrode structure for lithium-sulfur battery system

Abstract

The invention relates to a graphene electrode structure for a lithium-sulfur battery system. The electrode structure of the lithium-sulfur battery comprises a current collector and at least two layers of electrode compositions on the current collector, wherein each electrode composition comprises a graphene conductive material, a sulfur active material and a binding agent. By the electrode structure, an electrode can achieve high-capacity release (>3mAh / cm<2>) under the condition of high sulfur content (sulfur content on the electrode is more than 70%wt) and high sulfur carrying capacity (sulfur loading quantity on the electrode is more than 3mg / cm<2>); and moreover, due to gradient change of porosity in a thickness direction of the electrode and a blocking effect of a graphene stack structure on a surface of the electrode on multi-sulfur ion transmission, and stable circulation of the electrode in the lithium-sulfur battery system can be achieved.

Description

technical field [0001] The invention belongs to the fields of electrochemistry and batteries, and in particular relates to a graphene electrode structure design and preparation method for lithium-sulfur battery cathodes. Background technique [0002] At present, commercial lithium-ion batteries are mainly made of lithium cobaltate, lithium iron phosphate, and nickel-cobalt-manganese ternary materials. The development of their energy density has basically reached the theoretical limit of their materials, generally lower than 300Wh / kg, and there is little room for further improvement. Small. In order to make secondary batteries meet the needs of wider applications, such as power batteries and large energy storage batteries, researchers are extensively looking for and researching a new generation of secondary batteries with higher specific energy. The positive electrode material of lithium-sulfur battery is sulfur material, the theoretical specific capacity is 1675mAh / g, the n...

AI Technical Summary

Problems solved by technology

First of all, elemental sulfur and the discharge product lithium sulfide are electron and ion insulators at room temperature, which limits the utilization rate and rate performance of sulfur in the battery discharge process, especially when the electrode has a high sulfur content (sulfur content on the electrode > 70%wt) And high sulfur loading (sulfur loading on the electrode> 3mg / cm 2 ) case, this phenomenon is more serious

Secondly, sulfur will experience 17% volume expansion and contraction during the charge and discharge process, resulting in changes in the structure of the electrode material and separation from the metal current collector, resulting in capacity fading during the cycle.

Third, lithium polysulfide, an intermediate product of sulfur material discharge, is easily soluble in the electrolyte, and will diffuse to the negative lithium surface to react to form lithium sulfide and lithium disulfide, resulting in corrosion of the lithium negative electrode surface and loss of electrochemically active materials, resulting in Rapid capacity decay during cycling

However, these technical applications will introduce a conductive material composite layer that does not contain sulfur active materials into the electrode structure, resulting in a decrease in the sulfur content of the active material in the pole piece, which is not conducive to the improvement of the energy density of the pole piece

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