Lithium-sulfur battery positive-pole composite material with imitated cellular structure and preparation method thereof

Abstract

The invention discloses a lithium-sulfur battery positive-pole composite material with an imitated cellular structure and a preparation method thereof. In the positive-pole composite material, a conductive polymer film layer and nanometer oxide inlaid inside the conductive polymer film layer form a cell membrane, an elemental sulfur particle serves as a cell nucleus, and the three portions jointly form the imitated cellular structure. The composite material is prepared by conducting ultrasonic dispersion on the elemental sulfur particle and the nanometer oxide in water in the presence of a surface active agent, adding a conductive polymer monomer and an acid solution, performing even stirring and then adding an oxidizing agent to perform stirring reaction. The preparation method is simple in process, low in cost, low in energy consumption, controllable in sulfur content and good in repeatability and enables large-scale production to be easily achieved. The composite material is made into a lithium-sulfur battery positive pole, loss of active substances in the charging-discharging process can be effectively inhibited, improvement of the specific discharge capacity of a battery material and the utilization ratio of the active substances is facilitated, and accordingly the battery cycle performance is greatly improved.

Description

technical field [0001] The invention relates to a lithium-sulfur battery positive electrode composite material with a cell-like structure and a preparation method thereof, in particular to a positive electrode composite material in which a nano-oxide is embedded in a conductive polymer shell structure to form a cell-like membrane structure coated sulfur particles and its preparation The method belongs to the technical field of electrochemical energy. Background technique [0002] Since entering the 21st century, with the changes of the times, energy storage technology has provided infinite and broad application possibilities. As the main direction of energy storage technology, high-performance batteries are not only in the support and core position in the new energy field, but also in military and aerospace Therefore, the development of high-performance batteries has become an indispensable and important part of today's technological development. [0003] Currently commerci...

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Problems solved by technology

[0005] (1) Elemental sulfur at room temperature as S 8 It exists in the form of a typical electronic and ionic insulator, and its conductivity is about 5×10 -30 S / cm, when used as a battery active material, the utilization rate is not high

[0006] (2) Lithium polysulfide Li, an intermediate product of sulfur in the battery discharge process 2 S x (3≤x≤8), easily soluble in organic solvents, resulting in loss of active material, lower specific capacity, and poor cycle stability

In addition, the long-chain lithium polysulfide dissolved in the organic solvent will move from the positive electrode to the negative electrode, and undergo a reduction reaction with the negative electrode lithium to form a short-chain polysulfide, and the formed short-chain polysulfide will diffuse to the positive electrode and the negative electrode. The dissolved sulfide ions react to form long-chain lithium polysulfides, and this cycle, the so-called shuttle effect, leads to low battery charge and discharge efficiency; in addition, the lithium polysulfides formed on the negative electrode will also be reduced to Li 2 S and Li 2 S 2 , deposited on the surface of lithium metal, which reduces the ion and electronic conductivity and affects the electrochemical performance of the battery

[0007] (3) During the charge and discharge process, due to the difference in density between sulfur and the intermediate product lithium polysulfide, the volume of the positive electrode material will expand and shrink during the oxidation-reduction reaction process, and the volume change is as high as 80%, so that the electrode material is charged and discharged. Collapse during discharge, which affects the stability of the electrode and aggravates the attenuation of the specific capacity of the battery

Lithium-sulfur battery cathode materials have made great progress in recent years, but there are still some problems in related work: low sulfur loading of composite materials leads to low battery energy density, poor electronic conductivity leads to low cycle stability and low capacity retention , and the existing process is relatively complicated, the process cost is high, and the battery stability is poor

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