Study On Preparation And Performance Of Molybdenum-doped Carbon Aerogel As Cathode Material For Lithium-sulfur Batteries

Lithium-sulfur batteries have gained great attraction. Sulfur cathodes have the superiority of high theoretical gravimetric energy densities (2600 Whk·g-1 ), high theoretical capacity (1675 mAh·g-1), the non-toxicity, cheap and abundance. But some indigenous problems of sulfur hampered the practical application of Li-S battery, such as the insulativity of sulfur and the dissolvability of lithium polysulfide, which causes a series of problems for Li-S battery. In order to solve the above mentioned issues, we conducted deeply study of sulfur/carbon composites, and prepared Mo-decorated coaxial nanocable carbon aerogel. The as-prepared samples were characterized by transmission electron microscopy, scanning electron microscopy, thermogravimetric analysis, X-ray powder diffraction, X-ray photoelectron spectroscopy, CV and EIS.Due to the structure guide of CNT,we prepared the interconnected coaxial nanocable structure carbon aerogel (CNCA). Molybdenum compounds embedded in CNCA have the good electrically conductive, large surface area, porosity property,the special function of anchoring and adsorbing sulfur and polysulfide. The results indicate, the composites of coaxial nanocable structure as cathode for lithium-sulfur batteries exhibit improved electrochemical performances, such as high initial capacity,good cycle performance, batter rate performance and low impedance.MoS2-decorated coaxial nanocable carbon aerogel have high initial capacity, good cycle performance, rate performance and electronic conductivity. The results can be attributed to the contribution of channel, large surface area, small pore size and special anchoring function of molybdenum disulfide. The MoS2-8/CNCA/S composite delivers a discharge capacity of 1343 mAh-g-1 at 0.2C with the capacity retention of 81% after 200 cycles. Even at 5C, the electrode presents high discharge capacity of 723 mAh·g-1.Meanwhile, the MoO2-decorated coaxial nanocable carbon aerogel(MoO2-n/CNCA)was prepared by MoO2 nanoparticles embedding and distributing in CA sheath of CNCA. The MoO2-6/CNCA/S composite delivers a discharge capacity of 1308 mAh·g-1 at 0.2C with the capacity retention of 80% after 200 cycles. Even at 5C, the electrode presents high discharge capacity of 686 mAh·g-1.