Synergistic Effect between Monodisperse Fe₃O₄ Nanoparticles and Nitrogen-Doped Carbon Nanosheets to Promote Polysulfide Conversion in Lithium–Sulfur Batteries

Abstract

Effective fabrication of electrocatalysts active in anchoring and converting lithium polysulfides is critical for the manufacturing of high-performance lithium–sulfur batteries (LSBs). In this study, original Fe3O4 nanospheres with diameters close to 12 nm were finely dispersed over a porous nitrogen-doped carbon matrix by the freeze-drying method to produce a three-dimensional composite material (nano-Fe3O4/PNC) suitable for application as a sulfur host in LSBs. Nano-Fe3O4/PNC loaded with sulfur (S@nano-Fe3O4/PNC) was used as a cathode in a Li–S cell, whose initial discharge specific capacity reached 1256 mA h g–1 at a 0.1 C rate. After 100 charge–discharge cycles at a 0.2 C rate, the reversible capacity of S@nano-Fe3O4/PNC remained at 745 mA h g–1, demonstrating a capacity retention rate of 70%. Importantly, a high Coulombic efficiency of more than 99% was achieved, indicating effective inhibition of the polysulfides’ “shuttle effect” by nano-Fe3O4/PNC. The use of electrolytes containing lithium nitrate further reduces the “shuttle effect” of polysulfides. This study demonstrates the synergistic effect between metal oxide nanoparticles and N-doped carbon, which plays an important role in promoting the adsorption and conversion of polysulfides in LSBs.

Efficient immobilization and bidirectional catalysis of polysulfide conversion by FeCoP quantum dots for lithium–sulfur batteries

“…Also, their diffraction peaks are possibly masked by the peak signals of the graphite. 23 As seen from the Raman spectra in Fig. 2b, the two Scheme 1 Schematic of the synthetic process of the NCS, FeCo-NCS and FeCoP-NCS samples.…”

“…Meanwhile, the inorganic species with stronger polar-polar interactions were also proposed for use as xatives and catalysts to prevent the shuttle effect and improve the redox kinetics of polysuldes. In search of efficient and reliable catalysts, various highly polar metal-based materials such as oxides (MnO 2 and Fe 3 O 4 ), 23 carbides (MXene), 24 nitrides (Co 4 N), 25 suldes (Co 3 S 4 ) 21 and metal-organic frameworks (Ni-MOFs) 26 have been explored as promising candidates for preventing polysulde diffusion and accelerating transformation kinetics. However, most of those catalysts only showed unidirectional catalysis for the discharge process from S 8 to Li 2 S, and the charging process from Li 2 S to S 8 was hindered by the high reaction energy barrier.…”

Unraveling Polysulfide's Adsorption and Electrocatalytic Conversion on Metal Oxides for Li‐S Batteries

“…Another case is MOs catalysts serving as additives, with carbonaceous materials as sulfur host. [ 16 , 137 ] MOs are used to decorate the surface of the carbon host, this case is much more common. However, due to the inherent low conductivity of MOs, the LiPSs on MOs will go through an “adsorption‐diffusion‐conversion” process, in which diffusion is an additional step with sluggish kinetics.…”

Enhanced lithium polysulfide adsorption on an iron-oxide-modified separator for Li–S batteries

“…18 Polar metal oxides (such as Ti 4 O 7 , 19 V 2 O 5 , 20 CoFe 2 O 4 21 ) show stronger chemical interactions with LiPSs and higher catalytic activity towards them than does non-polar carbon. 22–24 The polar bonds between metal cations and oxygen anions could provide enough polar active sites to anchor LiPSs. 25,26…”

“…18 ) show stronger chemical interactions with LiPSs and higher catalytic activity towards them than does non-polar carbon. [22][23][24] The polar bonds between metal cations and oxygen anions could provide enough polar active sites to anchor LiPSs. 25,26 Iron oxides (IOs) are recognized as candidates for Li-S batteries due to their relatively low cost, excellent catalytic activity and desirable theoretical capacity.…”