| The global energy consumption is rapidly increasing due to the economic growth and population expansion.The large-scale usage of fossil fuels since Industrial Revolution has given rise to a series of issues such as energy shortage and environmental pollutions.Therefore,it is of extreme urgency to develop the clean renewable energy sources.Noticeably,most of the renewable energy sources cannot be taken and used immediately,the demand on high-energy-density storage system is thus proposed,in which various secondary battery systems have attracted the significant attention from both academic and industrial communities because of their capability of controlled charge/discharge.With its remarkable characteristics of an energy density up to 2600 Wh kg-1,lithium-sulfur batteries have become one of the most promising energy storage systems.However,it is found that lithium-sulfur batteries have serious problems such as low electrical conductivities of sulfur and its discharge products,slow kinetical processes,shuttle effect,volume expansion and so on,which hinders their large-scale applications.In view of the issues existing in the cathode of lithium-sulfur batteries,a core-shell structured BaTiO3@SiO2@C composite is controllably synthesized through the solution chemistry approaches,which can be used as the ferroelectric immobilizer for the cathode of lithium-sulfur batteries.Consequently,similar synthesis method is adopted to synthesize ZnO@SiO2@C and SrTiO3@SiO2@C composites as controlled samples,acting as piezoelectric comparison group and unpolarized comparison group,respectively,so the in-depth analysis on the mechanism of ferroelectric nanoparticles in lithium-sulfur batteries is performed.The composite materials were prepared by a simple and controllable method,and the as-synthesized products have uniform morphology,stable structure and abundant pore size.Under the multiple effects including physical and chemical confinements from the core-shell structure on polysulfides,the suppression of shuttle effect by piezoelectric potential of ferroelectric nanoparticles,the adsorption of polysulfides by ferroelectric nanoparticles,the lithium-sulfur batteries with BaTiO3@SiO2@C composite in the cathode achieved excellent electrochemical reaction kinetics,good rate performance and cycling stability.The discharge capacity of first cycle reached 1225 mA g-1,and the average decay rate per cycle across 300 cycles was as low as 0.04%.Through the preparation of ZnO@SiO2@C and SrTiO3@SiO2@C composites,the versatility of the preparation method is further demonstrated.Moreover,by comparing their electrochemical performances to that of BaTiO3@SiO2@C composite,the multifunctional properties of ferroelectric nanoparticles in the cathode of lithium-sulfur batteries are systematically illustrated.This work may shed light on the practical applications of lithium-sulfur batteries in the future. |
