Search

Pyrite FeS2 is a promising alternative to typical intercalation cathodes for rechargeable lithium-ion batteries (LIBs) by virtue of its extremely high theoretical capacity. However, the inferior rate capability and fast capacity degradation caused by the sluggish reaction kinetics and large volume expansion upon lithiation greatly hinder its practical application. Herein, a chemical crosslinking strategy is developed for the synthesis of the yolk-shell pyrite FeS2@porosity-rich sulfur-doped carbon nanonetworks (FeS2@C NNs) as cathode materials for high-performance LIBs. The 3D nanonetwork structure constructed by tight covalent connection of carbon shells can act as highways to facilitate the electron transport kinetics, while the well-orchestrated internal cavities of the yolk-shell nanostructure provide large void space to accommodate the volume expansion of pyrite FeS2. In addition, the porosity-rich characteristic of carbon shells ensures fast pathways for the Li+ diffusion across the shells. As a result, the yolk-shell FeS2@C nanonetworks exhibit excellent high-rate capability (353 mAh g−1 at 10 C) and exceptionally long lifespan of 1000 cycles with a high capacity of 435 mAh g−1 at a large current density of 5 C, which is by far the best of pyrite FeS2-based cathodes for LIBs.

Herein, we report a general and template-free protocol to construct novel yolk–shell metal@carbon nanospheres based on confined interfacial copolymerization, which greatly simplifies the synthetic route, yields uniform nanospheres with controllable diameters, and results in highly porous carbon shells. The yolk–shell Au@carbon shows improved adsorption capacity and high catalytic ability due to the synergistic effect of Au and the porous carbon shell.

Lithium-sulfur (Li-S) batteries, based on the redox reaction between elemental sulfur and lithium metal, have attracted great interest because of their inherently high theoretical energy density. However, the severe polysulfide shuttle effect and sluggish reaction kinetics in sulfur cathodes, as well as dendrite growth in lithium-metal anodes are great obstacles for their practical application. Herein, a two-in-one approach with superhierarchical cobalt-embedded nitrogen-doped porous carbon nanosheets (Co/N-PCNSs) as stable hosts for both elemental sulfur and metallic lithium to improve their performance simultaneously is reported. Experimental and theoretical results reveal that stable Co nanoparticles, elaborately encapsulated by N-doped graphitic carbon, can work synergistically with N heteroatoms to reserve the soluble polysulfides and promote the redox reaction kinetics of sulfur cathodes. Moreover, the high-surface-area pore structure and the Co-enhanced lithiophilic N heteroatoms in Co/N-PCNSs can regulate metallic lithium plating and successfully suppress lithium dendrite growth in the anodes. As a result, a full lithium-sulfur cell constructed with Co/N-PCNSs as two-in-one hosts demonstrates excellent capacity retention with stable Coulombic efficiency.