Construction Of Heterostructures Of Co,Zn,Mo-Based Transition Metal Compounds And Its Application In Lithium-Sulfur Batteries

Recently,energy storage devices have been demanding higher standards for rising living standards and the rapid development of portable electronics and electric vehicles.Due to high energy density,low price,and environmental friendliness,lithium-sulfur batteries have attracted the attention of researchers.However,the application process of lithium-sulfur batteries is hindered by some inherent problems such as the insulating properties of sulfur(S₈)and lithium sulfide(Li₂S),the shuttle effect caused by high-order polysulfides dissolution,slow reaction kinetics,and low utilization of active materials.To solve the above problems,based on the role of"chemical adsorption"or"catalytic conversion",this paper constructs3D-MoC/MoSe₂,ZnSe/CoSe/CNT as the lithium-sulfur batteries host materials and Co/CoO modified separator,which effectively improves the electrochemical performance of the lithium-sulfur battery.The concrete analysis is as follows:In order to improve the reaction kinetics during the charging/discharging process of lithium-sulfur batteries,a honeycomb-shaped 3D-MoC/MoSe₂ heterostructure was constructed by combining the casting and selenization strategy.After the sulfurization process,the composites were used as the cathode material.3D-MoC/MoSe₂ plays a synergy effect,in which 3D-MoC catalyzes the process from S₈ to Li₂S₄,and3D-MoSe₂ catalyzes the progress from Li₂S₄ to Li₂S.The feasibility of stepwise catalysis is discussed,which effectively improves the reaction process kinetics and significantly improves the electrochemical performance of lithium-sulfur batteries.The batteries exhibited a high initial discharge capacity of 919.2 m Ah g^-1 at 0.5C and the capacity retention rate was 85%after100 cycles.In order to suppress the shuttle effect caused by the high-order polysulfides dissolution during the reaction of the lithium-sulfur battery,ZnSe/CoSe/CNT derived from the metal-organic framework(MOF)was constructed by co-precipitation and high-temperature selenization method.After the sulfurization process,the composites were used as cathode material for Lithium-sulfur batteries.ZnSe/CoSe/CNT combines the strong adsorption effect of ZnSe/CNT for polysulfides and the high catalytic effect of CoSe/CNT for polysulfides,alleviating the shuttle effect during the reaction process,and thus delivered excellent electrochemical performance.The batteries display a high initial discharge capacity of 1172.1 m Ah g^-1 and an outstanding capacity retention rate of 81%after100 cycles at 0.2C.In order to improve the utilization of sulfur,Co/CoO composites derived from metal-organic framework(MOF)were constructed by co-precipitation and low-temperature oxidation strategy.Then,an efficient and stable reaction interface was built by Co/CoO materials coated on PP separator.Taking advantage of the different characteristics of Coand CoO to polysulfides,adjusting various oxidation levels of Co/CoO composites,the utilization rate of active materials was greatly improved,and the conversion process of polysulfides was effectively accelerated.When the oxidation time was 90 min,the optimized electrochemical performance would be obtained.The battery exhibited a high initial discharge capacity of 1087.0m Ah g^-1 at 0.5 C and the capacity retention rate is 78%after 100 cycles.