Preparation And Electrochemical Properties Of Transition-metal Oxide/Sulfur Composite Cathode For Lithium Sulfur Battery

With the rapid development of society,the environmental-friendly lithium sulfur battery could replace lithium-ion battery as an alternative to supply the demands for high capacity reserve devices due to its high specific capacity.In this paper,TiO₂,Co₃O₄ and MnO₂ were prepared by appropriate methods,mixed with sulfur to be the new composite cathodes by a simple two-layer coating or heating methode and exhibit the advantages of good electrochemical performance and unique morphology in these transition-metal oxides,in hopes of screening out the promising cathode materials with excellent cycle stability,high specific capacity and stable discharge voltage.?1?TiO₂ nanofibers were prepared by the electrospinning method with an average size of 140 nm and mixed with sulfur by heating to be the composite cathode.The highest specific capacity was 520 mAh g^-1 at 0.5 C in TiO₂@S cathode containing 50 wt%sulfur.The discharge capacity of 460 mAh g^-1 was maintained over 100 cycles,showing good cyclic stability.Co₃O₄ materials were prepared by the electrospinning to be used in the lithium sulfur battery.The results of the morphology test indicated that the optimized preparation condition for Co₃O₄ was the PVP density of 16.7 wt%.In the electrochemical test,Co₃O₄@S cathode containing 50 wt%sulfur achieved the highest specific capacity of 800 mAh g^-1 at 0.5 C,and after 100 cycles,77% of the reserved capacity was maintained,showing good electrochemical performance.?2?MnO₂@GP composites were prepared by MnO₂ nanoplates uniformly grown on the surface of GP by water bath method and mixed with sulfur as the functional layer to be a double-layer composite cathode by two-step coating technique.The sulfur cathode with 52%MnO₂@GP achieved the high initial capacity of 1400 mAh g^-1 at 0.5 C.After 100 cycles,the capacity was still 600 mAh g^-1.And the capacity decay rate was 0.3%per cycle between 10 to 100 cycles,showing the good high specific capacity and good cycle stability.?3?MnO₂ nanowires grown on the surface of GP by the hydrothermal method were used to prepare MnO₂ nanowire@GP composites.A double-layer composite cathode with the MnO₂ nanowire@GP composites as the functional layer and carbon/sulfur active materials were prepared by the two-step coating technique.A initial specific capacity of 930 mAh g^-1at 0.5 C,after 100 cycles,62%the capacity retention of 580 mAh g^-1 and coulombic efficiency close to 100%had been obtained in the cathode with 30% MnO₂ nanowire@GP as the functional layer.