Lithium-sulfur battery, positive electrode and negative electrode materials of lithium-sulfur battery and preparation method thereof

Abstract

The invention discloses a lithium-sulfur battery, positive electrode and negative electrode materials of the lithium-sulfur battery and a preparation method thereof. The preparation method of the positive electrode and negative electrode materials of the lithium-sulfur battery comprises the following steps: (1) in a nitrogen atmosphere, heating graphene oxide to obtain reduced graphene; and (2) ina nitrogen atmosphere, respectively mixing the reduced graphene obtained in the step (1) with sulfur powder and lithium powder, then respectively carrying out heating reaction in the nitrogen atmosphere, and after the reaction is finished, respectively obtaining the lithium-sulfur battery positive electrode material and the lithium-sulfur battery negative electrode material. The prepared positiveelectrode material and negative electrode material of the lithium-sulfur battery are used for preparing the lithium-sulfur battery, the capacity of the lithium-sulfur battery reaches 400Wh/Kg, and after 160 cycles, the charging efficiency still reaches 98%.

Description

technical field [0001] The invention belongs to the field of lithium-sulfur batteries, and in particular relates to a lithium-sulfur battery, lithium-sulfur battery positive and negative electrode materials and a preparation method thereof. Background technique [0002] Lithium-sulfur batteries use sulfur as the positive electrode active material and lithium as the negative electrode. During discharge, the negative electrode reaction is that lithium loses electrons and becomes lithium ions, and the positive electrode reaction is that sulfur reacts with lithium ions and electrons to form sulfide. The potential difference between the positive electrode and the negative electrode reaction is the discharge voltage provided by the lithium-sulfur battery. The theoretical discharge mass specific capacity of sulfur is 1675 mAh / g, the theoretical discharge mass specific capacity of lithium is 3860 mAh / g, and the theoretical discharge voltage of a lithium-sulfur battery is 2.287 V. Wh...

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Problems solved by technology

At the same time, lithium-sulfur batteries have the following problems: (1) The electronic conductivity and ionic conductivity of elemental sulfur are poor, and the conductivity of sulfur materials at room temperature is extremely low (5.0×10 -30 S cm -1 ), the final product of the reaction Li 2 S 2 and Li 2 S is also an electronic insulator, which is not conducive to the high rate performance of the battery

(2) The intermediate discharge products of lithium-sulfur batteries will dissolve into the organic electrolyte, increasing the viscosity of the electrolyte and reducing the ion conductivity

(3) The densities of sulfur and lithium sulfide are 2.07 and 1.66 g cm, respectively -3 , there is a volume expansion / contraction of up to 79% during charge and discharge, this expansion will lead to changes in the morphology and structure of the positive electrode, resulting in the detachment of sulfur from the conductive framework, resulting in capacity attenuation, and the huge volume change will destroy the electrode structure

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