Synthesis And Study On The Cathode Materials Of Lithium-sulfur Batteries

Lithium sulfur?Li-S?batteries is considered as one of the most promising candidates for next-generation electrochemical devices and caught intensive attention due to their high specific capacity,low cost and environmental friendliness.However,the ultralow electronical conductivity of sulfur,shuttle effect of intermediate polysulfides in electrolyte and volume expansion during the discharge process lead to low utilization and poor cycle stability of lithium-sulfur batteries,which greatly suppressed the practical application of Li-S batteries.In this research work,we mainly focus on how to overcome the problems above,the related research content and conclusions are as follows:?1?Carbon nanotube-nickel oxide/sulfur?CNT-NiO/S?composites were prepared by hydrothermal and thermal treatments.The hybrids combind the high conductivity of CNT and stronger absorbability of NiO to enhance electrochemical performance for sulfur electrode materials.The CNT-NiO/S electrode delivers an initial reversible discharge capcacity of 952 mAhg^-1 and retains 609 mAhg^-1 after 160th discharge at 0.1C,the coulombic efficiencies 99.4%before the first 100 cycles.?2?Graphene not only has good conductivity as CNT,but also has great flexibility,which can effectively reduce the volume expansion of S during discharge.In this chapter,we prepared reduced fluorinated graphene?RFG?via simple hydrazine vapor reduction of fluorinated graphite.The reduced fluorinated graphene-nickel oxide/sulfur?RFG-NiO/S?composites are prepared via similar method as?1?,the hybrids not only has strong physical adsorption and chemical adsorption of S and lithium polysulfides but also reliever the volume of sulfur in the discharge process to some extent so as to increases the utilization of active material.The composite electrode delivers an initial high reversible discharge capcacity of952 mAhg^-1 and retains more than 600 mAhg^-1 at 110th discharge at 0.1C,and 381 mAhg^-1 at200th discharge at 0.5C,which shows excellent electrochemical performance.