Research On 3D Cathode Materials Of The Novel Lithium-polysulphide Battery

At present,lithium sulfur battery is one of the most promising storage batteries with sulfur as a cathode and metallic as an anode.Sulfur?S?has a large theoretical specific capacity of 1675 mAhg^-1 with these advantage of abundance,low cost and environmental friend.Combined with a metallic lithium,lithium sulfur batteries possess a high theoretical energy density of 2600 Wh Kg^-1.However,sulfur and its discharging product Li₂S are insulating,which should be composited with conductive materials,like S/C composite.The preparation process of the S/C composite is complex,including repeated grinding and long-time fusion process.Secondly,sulfur in the S/C composite is hard to achieve homogeneous distribution,resulting in the uncomplete demonstration of sulfur in capacity.Lastly,the utilization of current collector,conductive additive and binder decreases the energy densty of lithium sulfur battery.So lithium-polysulfide battery attracts some researchers'focus and research,using dissolved lithium polysulfide as an active material and three-dimensionally flexible carbon materials as cathode electrodes.N,O-codoped three-dimensional?3D?carbon nanotubes forest/carbon cloth?CNTs/CC?and carbon nanosheets/carbon cloth?CNSs/CC?were synthesized as lithium-polysulfide battery electrodes through a facile templete methode in this thesis.The main research contents and results are as follow:?1?Via a wet chemical process,ZnO nanorods array was grown on carbon cloth.The polydopamine formed a coating layer on the ZnO nanorods array using dopamine as carbon source.After calcinated and acid washing,An N,O-codoped 3D CNTs/CC was attained.The highly conductive and hereroatom-doped composite as a lithium-polysulfide battery electrode shows rapid charge transfer,decreased polarization and improved reversibility of Li₂S/Li₂S_x/S.Lithium-polysulfide battery with CNTs/CC achieved a high capacity of 1200 m Ahg^-1 at 0.1 C and 900 m Ahg^-1 at0.5 C.After 300 cycles at 0.5 C,a capacity of 623 m Ahg^-1 was still abtained.?2?Via a wet chemical process,ZnO nanosheets was grown on carbon cloth.The polydopamine formed a coating layer on the ZnO nanosheets using dopamine as a carbon source.After calcinated and acid washing,an N,O-codoped 3D CNS/CC was attained.Large specific-surface-area and N,O-codoped CNS/CC exibited good electrochemical performance,structural stability and strong adsorption to polysulfides.The lithium-polysulfide battery with CNSs/CC demonstrated rapid charge transfer,decreased polarization and improved reversibility of Li₂S/Li₂S_x/S.At 0.1 C,the cell displayed a capacity of 900 m Ahg^-1.After 250 cycles at 0.5 C,a capacity of⁵00mAhg^-1was still remained.