Lithium-ion battery carbon-sulfur composite cathode material and preparation method thereof

Abstract

The invention discloses a carbon-sulfur composite positive electrode material of a lithium-ion battery and a preparation method of the material. The positive electrode material comprises a shell layer and a nuclear layer, wherein the shell layer comprises a conducting polymer layer; the nuclear layer comprises a sulfur layer; and a nano conducting material is uniformly distributed in the sulfur layer and comprises more than one dotted nano conducting particles and more than one linear and / or piece-shaped conducting nano materials. The preparation process comprises the following steps of: (1) after uniformly mixing the nano conducting material and the sublimed sulfur, carrying out insulating treatment in closed environments with the temperatures of being 120-300 DEG C and 300-500 DEG C in sequence, and then naturally cooling to obtain the powder; and (2) carrying out ball-milling treatment on the powder obtained by the step (1), wrapping the powder by the conducting polymer, then cleaning, and drying under the condition with the temperature of being 80-120 DEG C, thus obtaining a target product. The invention has the advantages that the service life of the sulfur positive electrode material of the lithium battery can be effectively prolonged, the cycling performance of the sulfur positive electrode material can be improved, the single carrying amount of the sulfur can be improved, and the preparation process is simple and high-efficiency, and is low in cost and easy in large-scale production.

Description

technical field [0001] The invention particularly relates to a novel lithium-ion battery carbon-sulfur composite cathode material and a preparation process thereof. technical background [0002] The trend of miniaturization, high energy, and portability of electronic appliances, the development of space technology, the demand for national defense equipment, and the research and development of electric vehicles have higher requirements for the performance of lithium-ion batteries. The improvement of lithium-ion battery performance mainly depends on the improvement of energy density and cycle life of lithium intercalation electrode materials, among which elemental sulfur has the highest specific capacity. In Li / S batteries, it is assumed that the sulfur at the positive electrode reacts completely to form Li 2 S, that is, a battery reaction occurs (S + 2Li = Li 2 S), the corresponding positive electrode theoretical specific capacity is 1 675mAh / g, the theoretical specific ene...

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Problems solved by technology

However, Li / S batteries with a positive electrode of 100% sulfur cannot be charged and discharged at room temperature, because the ionic conductivity and electronic conductivity of sulfur are very low, resulting in poor electrochemical performance and low utilization of sulfur in the electrode. Generally, compounding sulfur with carbon or other conductive materials can solve the problem of poor conductivity

Lithium polysulfide produced during the charging and discharging process of lithium-sulfur battery is easily soluble in organic electrolyte, which gradually reduces the active material of the electrode, and due to the shuttle principle, the dissolved lithium polysulfide will pass through the diaphragm and reach the negative lithium sheet of the battery, and the generated sulfide Lithium and other products have poor conductivity and are insoluble, which will cause corrosion of the negative electrode of the battery and increase the internal resistance of the battery, resulting in poor cycle performance of the battery and gradual decline in capacity. During the cycle, the volume deformation of the sulfur electrode in lithium-sulfur batteries is as high as 22%. , may cause microcracks inside the sulfur electrode

The existence of such microcracks and the insulating phase Li 2 The generation of S at the cracks destroys the integrity of the electrode and eventually aggravates the capacity fading of the Li-S battery

In addition, the sulfur loading in traditional sulfur-carbon composites formed by simple compounding of sulfur and carbon generally cannot be too high, otherwise it will affect its electronic conductivity and utilization of sulfur.

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