Home > News > Advanced energy materials: hierarchical porous carbon spheres modified by pyrite electrocatalyst designed at molecular level as lithium sulfur battery nanoreactor

Advanced energy materials: hierarchical porous carbon spheres modified by pyrite electrocatalyst designed at molecular level as lithium sulfur battery nanoreactor

wallpapers News 2020-08-05

lithium sulfur battery has high theoretical energy density (2600 WH / kg) theoretical specific capacity (1675 MAH / g) which is considered as a high specific energy battery with broad application prospects. However due to the slow reaction kinetics of sulfur conversion in the process of charge discharge the utilization rate of sulfur is not high the shuttle effect is serious. As a result the capacity of lithium sulfur battery is low the cycle stability is poor which greatly limits the practical application of lithium sulfur battery. Therefore how to reasonably design the electrocatalytic system realize the catalytic conversion of polysulfides efficiently stably under the condition of high sulfur loading improve the capacity life of lithium sulfur battery is one of the bottlenecks in the application development of lithium sulfur battery.

Liu Jian Wu Zhongshuai researchers of Dalian Institute of Chemical Physics Chinese Academy of Sciences developed a Fe1 XS modified nano reactor through molecular level design applied it to the cathode of lithium sulfur battery obtained excellent polysulfide catalytic activity cycle stability.

in the process of polymer resin synthesis metal precursors were directly added to the mixture resorcinol sulfide (RS) was used as the source of C s. The sulfur in RS acts as a lig binds to metal cations by complexation. After mixing Fe3 with ethanol / water solution containing RS a pink solution was obtained which proved the formation of [Fe3 – RS] complex. Then NH3 aqueous solution was added the solution turned dark brown due to the further formation of [Fe3 NH4 - RS] complex. With the addition of formaldehyde the polymerization reaction was initiated the Milky brown precipitate of [Fe3 NH4 - RS] - f resin was gradually formed in which Fe3 was evenly distributed. The final brownish color of the precipitate confirmed that Fe3 was evenly distributed in [Fe3 NH4 – RS] - f resin by complexing. The brown resin was then thoroughly mixed with melamine (as a source of n) finally carbonized in a 5% H2 / AR mixture at 900 ° C. During the carbonization process large mesoporous cavities well dispersed Fe1 XS nanoparticles gradually formed in situ in the carbon spheres thus forming hierarchical porous Fe1 XS NC nanospheres. At the same time N in melamine can be used as the fixed point of Fe to control the dispersion of Fe1 XS. Fe1 XS NC has higher specific surface area (627 M2 · g-1) larger pore volume (0.41 cm3 · g-1) enhanced adsorption electrocatalytic transformation to polysulfides. The large mesopores generated in situ in the carbon spheres can accommodate up to 75% of the high sulfur load maintain volume change during the charge / discharge cycle improve ion / mass transfer. Cai Qiong's team of Surrey University predicted theoretically the adsorption performance of Fe1 XS NC for polysulfides which was confirmed by experiments. Subsequently the electrocatalytic activity of Fe1 XS NC was tested. The results show that Fe1 XS NC is an efficient nano reactor for sulfur loading. Therefore the Fe1 XS NC nanoreactor performed very well as the cathode material for lithium sulfur battery. After 200 cycles at 0.5 C it showed a high initial capacity of 1070 MAH g-1 with almost no capacity loss. In addition even at a high sulfur load of 8.14 mgcm-2 the obtained lithium sulfur battery still showed significantly enhanced rate capability cycling capability.

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