| Lithium-sulfur batteries have a high specific capacity,and as their main active material,S has a wide range of sources,low prices,a high amount of earth reserves,and environmental friendly pollution-free,with good application potential and prospects.However,the poor cycle life of lithium-sulfur batteries limits its industrialization,and its lower cycle stability is mainly due to:?1?the insulation of the active substance S and the polysulfide of the discharge product;?2?the shuttle effect leads to the loss of active substances,The electrical performance drops rapidly;?3?The volume expansion rate of S causes the electrode material structure to powder;?4?Lithium dendrite.In response to these problems,this paper modified the titanium dioxide material and applied it to the electrode materials and separators of lithium-sulfur batteries.By inhibiting the shuttle effect of polysulfide,the energy storage properties of the battery were improved,and the stability mechanism of the battery was explored.First of all,the porous TiO2 is modified to combine with SnO2,NiO,and Pt oxides to increase the TiO2 conductivity and increase the specific capacity of the composite.At the same time,this porous structure of TiO2 can limit the volume expansion of other oxides generated during the cycle and enhance the cycle stability of the battery.By changing the doping amount of SnO2 in the composite,SnO2-TiO2 composites with 5%,10%and 15%SnO2 mass fractions were prepared.The results show that the initial discharge specific capacity of 5%TiO2-SnO2 is339.4mAh·g-1 at a current density of 200 mAhg-1,and the specific capacity of the battery is147 mAh·g-1 at 300 cycles,which shows the best performance.The first discharge specific capacities of TiO2,SnO2-TiO2,NiO-TiO2,Pt-TiO2 oxide composites were:259.6mAh·g-1,339.4mAh·g-1,284.5mAh·g-1,271.7mAh·g-1;SnO2-TiO2 had The highest specific capacity performance.Based on the above inorganic materials modified porous TiO2,this paper continues to try to modify the porous TiO2 by the conductive polymer polypyrrole?PPy?,and the composite material is applied to the positive electrode of a lithium-sulfur battery.The results show that the initial discharge specific capacity of TiO2-PPy-S is 564.2mAh·g-1;after 300 cycles,the remaining capacity is 61.5%,and its cycle stability is greatly improved.The excellent performance of the battery is mainly due to the one-dimensional through-hole structure of the TiO2-PPy electrode material,which facilitates the transfer and diffusion of sulfide molecules;the strong adsorption of TiO2 on sulfide molecules effectively prevents the loss of active materials such as sulfides.At the same time,the conductivity of titanium dioxide and S is modified by compounding polypyrrole,and the ionic conductivity of the material is enhanced,thereby increasing the specific capacity and cycle stability of the electrode..While modifying the electrode material,the paper further studied the effect of the modification of the lithium-sulfur battery diaphragm on its operation stability.C-Ti O2 as a sulfide molecular adsorbent material is coated on the surface of a conventional porous PP film,and the discharge specific capacity is as high as 1334.7mAh·g-1 at a current density of 0.2C.After 50 cycles,the specific capacity still has a remaining amount of 78%.Good cycle stability.The specific capacity of the PP film was increased by about 200mAh·g-1 as compared with that of carbon black alone. |
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