A kind of preparation method of lithium-sulfur battery cathode material

Abstract

The invention relates to a preparation method of a lithium-sulfur battery positive electrode material, and belongs to the technical field of preparation of a battery positive electrode material. In order to solve the problem that a traditional sulfur-carbon composite material is easy to agglomerate during the preparation process and the grain size is difficult to control, the preparation method ofthe lithium-sulfur battery positive electrode material is provided. The method comprises the steps of adding an alkali metal element and a sulfur element into an organic solvent for reaction under acondition of inert gas protection to obtain a polysulfide organic solution; and taking a mixed liquid of a conductive polymer monomer and the polysulfide organic solution, adding an acid oxidizing agent solution, adjusting a pH value of the mixed liquid to be neutral or weak acid, and obtaining the sulfur / conductive polymer composite material after full reaction. By the preparation method, nanoscale or submicron-scale sulfur particle can be obtained, an effect of relatively narrow size distribution is achieved, the sulfur utilization ratio and the high-rate performance are improved, and the volume expansion phenomenon of the positive electrode material during the lithiation process is favorably reduced.

Description

Technical field [0001] The invention relates to a preparation method of a lithium-sulfur battery positive electrode material, and belongs to the technical field of battery positive electrode material preparation. Background technique [0002] Lithium-sulfur battery is a kind of lithium battery with sulfur element as the positive electrode of the battery, and the theoretical discharge specific capacity of elemental sulfur can reach 1675mAh / g, which is much higher than that of lithium-ion batteries widely used commercially. Therefore, the sulfur cathode active material is currently the cathode material with the highest specific capacity, and lithium is the metal element with the smallest relative atomic mass and the most negative standard electrode potential. Therefore, the lithium-sulfur battery has a high theoretical discharge voltage, a high theoretical specific discharge capacity, and a high theoretical specific energy. It is expected to meet the long-term development requireme...

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Problems solved by technology

[0003] According to prior art reports, the actual specific energy of lithium-sulfur batteries has reached 350Wh kg -1 ; But at this stage, lithium-sulfur batteries are facing a series of problems: there are mainly defects or problems in the following aspects: 1. Elemental sulfur and discharge product Li 2 S 2 / Li 2 S is an electronic and ion insulator, which increases the battery resistance and polarization; 2. The volume expansion of the positive electrode material during the discharge process causes the material structure to collapse and affects the cycle performance of the battery; The soluble polysulfides, due to the migration and reaction between the positive and negative electrodes due to diffusion, the "shuttle effect" of polysulfides occurs, resulting in the irreversible loss of active materials

For example, the Chinese patent (authorized announcement number: CN104701542B) discloses a preparation method of a composite positive electrode material for an all-solid-state lithium-sulfur battery, comprising dispersing conductive polymer monomers and elemental sulfur in water, adding hydrochloric acid and ammonium persulfate at 0-10 The polymerization reaction is carried out at ℃ to obtain a compound formed by the conductive polymer wrapping the elemental sulfur. After high-temperature heat treatment, the conductive polymer / sulfur composite positive electrode material is obtained. Due to the direct addition of elemental sulfur, agglomeration is prone to occur, and the particle size of the sulfur particles cannot be adjusted. , a defect that leads to unstable properties of the material

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