Synergistic Effect between Poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) Coated Sulfur Nano-Composites and Poly(vinylidene difluoride) on Lithium-Sulfur Battery

Abstract

In this work, the polyvinylpyrrolidone (PVP) coated sulfur nanoparticles (SNPs) are self-assembled with conductive poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS) to fabricate S@PEPS. After mixed with oil-based poly(vinylidene difluoride) (PVDF) and water-based polyacrylic latex (LA133), SNP/PVDF, S@PEPS/PVDF, SNP/LA, S@PEPS/LA cathodes with different interfacial properties are fabricated. The electrochemical results indicate that the S@PEPS based cathodes possess much better cycling stability than SNP based cathodes due to the conductivity and blocking effect of PEDOT:PSS shell. The S@PEPS/PVDF cathode exhibits much better cycling performance and rate property than that of S@PEPS/LA. The fitting data of EIS indicate that S@PEPS/PVDF cathode possesses smaller charge-transfer resistance and faster Li+ diffusion rate than S@PEPS/LA cathode. It can be proved that (1) the attraction between H+/Na+ in PEDOT:PSS and electronegative groups in PVP (C=O and N) and PVDF (F atom) help to maintain the stability of the cathode, enhance the electrochemical kinetics and suppress the dissolution of lithium polysulfide; (2) The outer PVDF binder glues KB on the surface of S@PEPS to form porous interfaces and benefit the e−/Li+ transmission. In brief, the electrode/electrolyte interfacial property built with S@PEPS and PVDF fulfill the synergistic effect of all the interfacial components and improve the electrochemical performance of S@PEPS/PVDF cathode.