Preparation of a carbon nanofibers-carbon matrix-sulfur composite as the cathode material of lithium-sulfur batteries

摘要

Sulfur is a promising cathode material for lithium batteries as it possesses high theoretical specific capacity and low cost. However, the practical electrochemical performance of lithium-sulfur batteries needs to be improved. In this work, a carbon nanofibers-carbon matrix-sulfur composite is synthesized to improve the electrochemical properties of lithium-sulfur batteries. The carbon matrix-sulfur composite is fabricated by deoxidizing the carbon precursor-sulfur composite. Morphology, structure and electrochemical properties of materials have been characterized and tested. Results show that the carbon matrix-sulfur composite envelops carbon nanofibers and sulfur is evenly distributed in the carbon nanofibers-carbon matrix-sulfur composite. In a carbon matrix-sulfur composite, sulfur chemically bonds with the carbon matrix. The chemical bonds form in the process of deoxidizing the carbon precursor-sulfur composite. In a carbon nanofibers-sulfur mixture, sulfur is dispersed on carbon nanofibers. In comparison with a carbon nanofibers-sulfur mixture electrode, the carbon nanofibers-carbon matrix-sulfur composite electrode exhibits higher discharge capacity and cycle stability. The better electrochemical performance is ascribed to the restriction for dissolution of lithium polysulfides through the adsorbability of the carbon matrix.