Adsorption-catalytic Effects Of Ferrous Slag On Polysulfides In Li-S Batteries

Lithium-sulfur（Li-S）battery is a promising next-generation energy storage system for high theoretical energy density(2600 Wh kg^-1).However,the shuttle effect of lithium polysulfides（Li PSs）restricts its further development and practical application.Recent studies have found and widely used the rich adsorption sites on the surface of polar transition metal oxides to realize the adsorption and catalytic conversion of Li PSs.However,complex synthesis process and high costs limit the large-scale application of transition metal compounds in Li-S batteries.As a common solid residue in the metallurgical process,Ferrous slag（FS）,mainly consisting of iron oxide,can exhibit potential adsorption and catalytic conversion of polysulfides in Li-S batteries.Moreover,it will also enable the reduction and high-value utilization of smelting slag,as well as alleviation on its environmental pollution.This paper uses FS obtained from the leaching of serpentine minerals as the sulfur host and interlayer for Li-S batteries,respectively.A series of electrochemical characterization methods were conducted to investigate the mechanism of FS on improving the performance of Li-S batteries.The research content mainly includes the following two aspects:（1）Using graphite（G）dispersion solution,FS and elemental sulfur（S）as raw materials,and ethanol as a dispersant,a series of G/FS/S composites were prepared by solution stirring and subsequent melt-diffusion methods for Li-S batteries.In the G/FS/S composites,G serves as a conductive network and provides conductive channels;FS is rich in Lewis acid-base active sites and exhibits strong adsorption to lithium polysulfides（Li PSs）,effectively relieving the shuttle of Li PSs while catalyzing the conversion reaction of Li PSs,which in turn improves the utilization of active sulfur and battery cycle stability.The experimental results show that the G/FS/S composite electrode exhibits a discharge specific capacity of 849 m Ah g^-1in the first cycle at 0.2 C and maintains a discharge specific capacity of 558m Ah g^-1 after 200 cycles.Even at a large current density of 1 C,the specific capacity of the battery remains 428 m Ah g^-1 after 200 cycles.（2）Based on the above work,considering that the introduction of FS as sulfur host material and its small specific surface area will reduce the total sulfur content.This work combines FS with conductive carbon to form a slurry by simple physical grinding.This slurry coats the cathode surface as a functional interlayer.The interlayer can achieve the physical block as well as the adsorption and catalysis of Li PSs,thereby increasing the utilization of active sulfur and improving the electrochemical performance of Li-S batteries.The experimental results show that the prepared G/S@acetylene black/FS（G/S@AB/FS）exhibits an initial discharge specific capacity of 1048 m Ah g^-1 at 0.2 C and a discharge specific capacity of 525 m Ah g^-1 after 200 cycles.The discharge specific capacity of the battery remains 493 m Ah g^-1 after 200 cycles at 1 C.