TiO₂ and Co Nanoparticle‐Decorated Carbon Polyhedra as Efficient Sulfur Host for High‐Performance Lithium–Sulfur Batteries

Abstract

Metal organic frameworks (MOFs)‐derived porous carbon is proposed as a promising candidate to develop novel, tailorable structures as polysulfides immobilizers for lithium–sulfur batteries because of their high‐efficiency electron conductive networks, open ion channels, and abundant central ions that can store a large amount of sulfur and trap the easily soluble polysulfides. However, most central ions in MOFs‐derived carbon framework are encapsulated in the carbon matrix so that their exposures as active sites to adsorb polysulfides are limited. To resolve this issue, highly dispersed TiO2 nanoparticles are anchored into the cobalt‐containing carbon polyhedras that are converted from ZIF‐67. Such a type of TiO2 and Co nanoparticles‐decorated carbon polyhedras (CCo/TiO2) provide more exposed active sites and much stronger chemical trapping for polysulfides, hence improving the sulfur utilization and enhancing reaction kinetics of sulfur‐containing cathode simultaneously. The sulfur‐containing carbon polyhedras decorated with TiO2 nanoparticles (S@CCo/TiO2) show a significantly improved cycling stability and rate capability, and deliver a discharge capacity of 32.9% higher than that of TiO2‐free S@CCo cathode at 837.5 mA g−1 after 200 cycles.

Yolk−Shell Nano ZnO@Co‐Doped NiO with Efficient Polarization Adsorption and Catalysis Performance for Superior Lithium−Sulfur Batteries

“…[16,17] For example, transition-metal oxides (TMOs) with abundant of active adsorption sites, which can chemically adsorb LiPSs and retain their capability, are regarded as effective sulfur hosts. [18][19][20][21][22][23] In addition, more and more TMOs have been certified to be beneficial to the conversion kinetics of intermediate LiPSs due to their catalytic effects. [6,[24][25][26] As typical TMOs, with the advantages of environmental friendliness and low cost, zinc oxide based nanomaterials have attracted lots of attention in the field of Li−S batteries.…”

Immobilizing Polysulfide by In Situ Topochemical Oxidation Derivative TiC@Carbon‐Included TiO2 Core–Shell Sulfur Hosts for Advanced Lithium–Sulfur Batteries

“…In addition, it is rarely reported in the previous studies toward using TiO 2 -based materials as the sulfur hosts. [22,28,52,62] Based on the above discussion, a dual chemical mediation mechanism for LiPSs, namely, strong surface polarpolar interaction coupled with thiosulfate/polythionate conversion, is demonstrated by the proposed TiC@C-TiO 2 composite in this study. The regulation mechanism of LiPSs is displayed in Figure 5d.…”

“…Nevertheless, the polar LiPSs still tend to move out of the cathode due to their weak interfacial interaction with nonpolar carbonaceous materials. [20] To this end, polar materials, such as heteratom-doped carbon, [21] transitional metal oxides, [22] metal sulfides, [23] metal nitrides, [24] metal carbides, [25] and metal borides [26] with a strong chemical affinity toward LiPSs, have been developed to effectively mitigate the notorious shuttle effect of LiPSs and achieve long-term cycling stability.…”

“…Many studies have demonstrated the effective entrapping of LiPSs using TiO 2 as a sulfur host and showed an improved electrochemical performance for Li-S batteries. [22,27,28] However, TiO 2 faces great difficulty in converting immobilized LiPSs to Li 2 S 2 /Li 2 S due to its poor electronic conductivity (10 −10 S cm −1 ), [29] thus weakening the redox reaction kinetics of sulfur species. On the other hand, as a congener of TiO 2 by substituting oxygen atom with carbon atom in the crystal lattice, TiC with a high conductivity (10 4 S cm −1 ) has also been widely investigated in the community of Li-S batteries.…”

Rational design of Co nano-dots embedded three-dimensional graphene gel as multifunctional sulfur cathode for fast sulfur conversion kinetics

“…Note that, since Co-NDs@G is developed through the calcination of ZIF-67@GO (N, Cocontaining precursor), it is difficult to directly distinguish the effects of Co and N on the battery performances. However, it was reported that Co nano-dots [44] and N-doped graphene [45] both can have positive effects on lithium-sulfur batteries. Moreover, our DFT calculations also showed that metal Co, Co-N-C, and Ndoped graphene sites exhibits high binding energy towards polysulfide species.…”