The Effective Design of a Polysulfide-Trapped Separator at the Molecular Level for High Energy Density Li–S Batteries

Abstract

In this work, the lightweight and scalable organic macromolecule graphitic carbon nitride (g-C3N4) with enriched polysulfide adsorption sites of pyridinic-N was introduced to achieve the effective functionalization of separator at the molecular level. This simple method overcomes the difficulty of low doping content as well as the existence of an uncontrolled form of nitrogen heteroatom in the final product. Besides the conventional pyridinic-N-Li bond formed in the vacancies of g-C3N4, the C-S bond was interestingly observed between g-C3N4 and Li2S, which endowed g-C3N4 with an inherent adsorption capacity for polysulfides. In addition, the microsized g-C3N4 provided the coating layer with good mechanical strength to guarantee its restriction function for polysulfides during long cycling. As a result, an excellent reversible capacity of 840 mA h g(-1) was retained at 0.5 C after 400 cycles for a pure sulfur electrode, much better than that of the cell with an innocent carbon-coated separator. Even at a current density of 1 C, the cell still delivered a stable capacity of 732.7 mA h g(-1) after 500 cycles. Moreover, when further increasing the sulfur loading to 5 mg cm(-2), an excellent specific capacity of 1134.7 mA h g(-1) was acquired with the stable cycle stability, ensuring a high areal capacity of 5.11 mA h cm(-2). Besides the intrinsic adsorption ability for polysulfides, g-C3N4 is nontoxic and mass produced. Therefore, a scalable separator decorated with g-C3N4 and a commercial sulfur cathode promises high energy density for the practical application of Li-S batteries.

Freestanding graphitic carbon nitride‐based carbon nanotubes hybrid membrane as electrode for lithium/polysulfides batteries

“…In addition, there was a new peak exhibited 284.8 eV, which can be attributed to the formation of CS bond. The chemical adsorption effect of g‐C 3 N 4 with polysulfides is also reflected in N1 s spectra (Figure 10C), which can be detected a slight positive shift of the CN bonds . The high resolution spectra of S2p is shown in Figure 10D and the binding energies of 162.7, 163.9, 167.5, and 168.9 eV apparently reflected to the LiS bond from lithium sulfide, SS bond from the sulfur, SO 3 2− from the decomposition of electrolyte, and SO (sulfates) by the oxidation of sulfur, respectively .…”

Coaxial Carbon/MnO2 Hollow Nanofibers as Sulfur Hosts for High‐Performance Lithium‐Sulfur Batteries

“…Common carbon materials involve porous/hollow carbon spheres, [17][18][19][20][21][22] carbon nanotubes [23,24] /nanofibers, [25] and graphene/graphene oxides/graphitic carbon nitride C 3 N 4 . [26][27][28] Althought he carbonaceous sulfur hosts indeed can exert good electronic conductivitya nd physical confinement of lithium polysulfides (LiPSs) within the nonpolar carbon frameworks to ac ertain degree, they still suffer from obvious capacity decay upon long-term cycling because of the weak interaction between polysulfides (PS) and carbon. [29] The polar materials have currently demonstrated high efficiency of chemisorption in suppressing the polysulfides huttlea nd then significantly improve long-term cycling stabilityd ue to their strongp olysulfide binding through chemical interactions.…”

Electrospun zeolitic imidazolate framework-derived nitrogen-doped carbon nanofibers with high performance for lithium-sulfur batteries

“…At the same time, the predominance of pyridine‐N in N‐CNFs means that it has an effective chemisorption capacity for the interatomic attraction of LPs during discharge‐charge processes. After cycled, the significant reducing in the strength of pyridine‐N can be attributed to the increased amounts of LPs adsorbed on the surface of the cathode . Based on the above analysis, the 3D porous structure and nitrogen‐doped in NCFs are main prerequisites for achieving a high‐performance LSB.…”