Controlling Structure And Chemical Composition Of Cathode Materials For Li-s Batteries

Lithium sulfur battery is one of the most cost-effective alternatives to meet the requirement of high energy density for power sources due to its high energy density and low cost,and it is thus considered as one of the most promising next-generation energy storage systems.The commercial application of lithium-sulfur batteries is still impeded by the unsatisfying cyclability due to the sluggish reaction kinetics and shuttling effect of polysulfide intermediates.I-doped carbon/sulfur electrode was prepared to improve the rate performance of Li-S batteries.The resultant composite electrode exhibits good high-rate charge-discharge capability with a high discharge capacity of 479 mAh/g at 3 C after 100 cycles.The excellent rate capability correlated with the iodine-doped carbon host of improved electronic conductivity as well as in situ anchored lithium iodide（LiI）with improved ionic conductivity.The LiI is anchored within the carbon host during the following charge/discharge cycles because the charge cut-off voltage of 2.6 V for the lithium sulfur battery is lower than the oxidation potential at the range of 2.9³.4 V vs Li/Li⁺for the LiI.This work offers an innovative,effective and facile method to ameliorate the electrochemical performance of lithium sulfur batteries.Cobalt nanoparticle-encapsulated carbon nanowire arrays on carbon cloth（CC@Co-CNAs）were prepared to enable the fast redox reaction kinetics of the lithium sulfur batteries.The nanowire array-decorated carbon cloth as sulfur host could provide highly exposed cobalt nanoparticle active sites,owing to the high length-diameter ratio of the prepared CC@Co-CNAs.The binding affinity between the cobalt nanoparticle-incorporated host materials and polysulfide intermediates is enhanced by Co-S bonds,which facilitates the redox reaction of active materials and consequently results in a better sulfur utilization for cathode especially under high sulfur loading.The lithium sulfur battery with CC@Co-CNAs as host materials delivers a high initial discharge capacity of1228 mAh g^-1 at 0.25 C,and a high initial discharge capacity of 807 mAh g^-1 at 1C with a low capacity fading rate of 0.06%per cycle during 300 cycles.Moreover,a discharge capacity of 958 mAhg^-1 at 0.1 C is achieved for the cell even with a sulfur loading as high as of 6.2 mg cm^-2.A novel three-dimensional clew-like N-doped multiwalled carbon nanotube（MWCNT）structure is obtained by carbonizing a Ni-based metal–organic complex.When developed as conductive sulfur-loading hosts for Li-S batteries,the interconnected open-ended MWCNT materials afford superior sulfur encapsulating and polysulfide intermediates immobilizing capabilities.Moreover,the porous graphitic carbon as a conductive matrix facilitates the electron transport and the reversible electrochemical reaction of active materials during cycling.Therefore,good cycling stability for 1000cycles with a low capacity decay rate of 0.053%per cycle and a high Coulombic efficiency up to nearly 100%at 0.2 C are achieved for the three-dimensional clew-like N-doped MWCNT/sulfur cathode material for Li-S battery applications.