Lithium-sulfur battery anode material and preparation method thereof and lithium-sulfur battery

Abstract

The invention discloses a preparation method of a lithium-sulfur battery anode material, and relates to the technical field of lithium-sulfur batteries. The preparation method comprises the following steps of 1 cotton dipping , wherein cotton is soaked in a hydrochloric acid solution containing zinc chloride for sealed heat preservation, the redundant solution is removed, and a mixture is dried and subjected to heat preservation treatment to obtain gray or brown solids; 2 porous carbon matrix preparing, wherein carbonization treatment and acidification treatment are conducted on the solids in sequence, and then washing, drying and calcining are conducted to obtain a porous carbon matrix; 3 carbon-sulfur composite material preparing, wherein the porous carbon matrix and elemental sulfur are heated together to synthesize the lithium-sulfur battery anode material. The invention further discloses the lithium-sulfur battery anode material prepared through the method and a lithium-sulfur battery. Compared with the prior art, the lithium-sulfur battery anode material obtained through the method has the advantages of being high in sulfur loading amount and capacity, good in cycle performance, simple in process and low in cost.

Description

technical field [0001] The invention relates to the technical field of lithium-sulfur batteries, in particular to a lithium-sulfur battery positive electrode material, a preparation method thereof, and a lithium-sulfur battery comprising the lithium-sulfur battery positive electrode material. Background technique [0002] Lithium-sulfur battery is a secondary battery with metallic lithium as the negative electrode and elemental sulfur as the positive electrode. During discharge, the negative electrode reacts as lithium loses electrons and becomes lithium ions, and the positive electrode reacts as sulfur reacts with lithium ions and electrons to form sulfide. The potential difference of the negative electrode reaction is the discharge voltage provided by the lithium-sulfur battery. The specific energy of lithium-sulfur batteries can theoretically reach 2600Wh / Kg, which is much larger than any commercial secondary batteries used at this stage. In addition to the advantages of...

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Problems solved by technology

[0004] First, the electronic conductivity and ionic conductivity of elemental sulfur are poor, and the conductivity of sulfur materials at room temperature is extremely low (the conductivity is only 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;

[0005] Second, lithium polysulfide, the intermediate discharge product of lithium-sulfur batteries, will dissolve into the organic electrolyte, increasing the viscosity of the electrolyte and reducing the ion conductivity.

Polysulfide ions can migrate between the positive and negative electrodes, resulting in the loss of active materials and a decrease in coulombic efficiency. In addition, due to the insulation of the deposited reaction products, further lead to battery performance degradation

[0006] Third, the final discharge product of lithium-sulfur batteries, Li 2 S n (n=1-2) Electronic insulation and insoluble in the electrolyte, deposited on the surface of the conductive framework, part of the lithium sulfide is separated from the conductive framework, and cannot be reacted into sulfur or high-order polysulfides through a reversible charging process, resulting in Great attenuation of capacity

[0007] Fourth, the densities of sulfur and lithium sulfide are 2.36 g cm -3 and 1.66g cm -3 , there is a volume expansion / contraction of up to 42% during charge and discharge, and this expansion will lead to changes in the morphology and structure of the positive electrode, leading to the detachment of sulfur from the conductive framework, resulting in capacity attenuation

[0009] However, the lithium-sulfur positive electrode material prepared by the method in the prior art has low specific surface area and small pore volume of the porous carbon matrix, so the sulfur loading capacity is not high, the battery capacity is not high, and the preparation method is cumbersome. The cost is high and cannot meet the actual needs

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