Various and critical electrocatalytic processes are involved during the redox reactions in the Li-S batteries, which extremely depend on the surface structure and chemical state. Recently, single-atom concept unlocks a route to maximize the use of surface-active atoms, however, further increasing the density of active site is still strictly limited by the inherent structure that single-atoms are only highly-dispersed on substrate. Herein, we provide a viewpoint that an elaborate facet design with single-crystalline structure engineering can harvest high-density surface active sites, which can significantly boost the electrocatalyst performance for excellent Li-S batteries. Specifically, the single-crystal CoSe₂ (scCS) exhibits three-types of terminated (011) facet, efficiently obtaining the surface with a high-rich Co³⁺–Se bond termination, in contrast with lots of surface grain boundaries and dangling bonds in polycrystalline CoSe₂. Surprisingly, the surface active sites concentration can reach more than 69%. As anticipated, it can provide high-density and high-efficient active sites, enormously suppressing the shuttle effect and improving the reaction kinetics via accelerating the conversion and deposition of polysulfides and Li₂S. This surface lattice strategy with element terminated mode is a promising approach for designing electrocatalyst effect-based energy system, not merely for Li-S batteries.

Molybdenum disulfide (MoS₂) has received enormous attentions in the electrochemical energy storage due to its unique two-dimensional layered structure and relatively high reversible capacity. However, the application of MoS₂ in potassium-ion batteries (PIBs) is restricted by poor rate capability and cyclability, which are associated with the sluggish reaction kinetics and the huge volume expansion during K⁺ intercalation. Herein, we propose a two-dimensional (2D) space confined strategy to construct van der Waals heterostructure for superior PIB anode, in which the MoS₂ nanosheets can be well dispersed on reduced graphene oxide nanosheets by leveraging the confinement effect within the graphene layers and amorphous carbon. The strong synergistic effects in 2D van der Waals heterostructure can extremely promote the electron transportation and ions diffusion during K⁺ insertion/extraction. More significantly, the 2D space-confinement effect and van der Waals force inhibit polysulfide conversion product dissolution into the electrolyte, which significantly strengthens the structural durability during the long-term cycling process. As anticipated, the as-synthesized the "face-to-face" C/MoS₂/G anode delivers remarkable K-storage performance, especially for high reversible capacity (362.5 mAh·g^-1 at 0.1 A·g^-1), excellent rate capability (195.4 mAh·g^-1 at 10 A·g^-1) and superior ultrahigh-rate long-cycling stability (126.4 mAh·g^-1 after 4000 cycles at high rate of 5 A·g^-1). This work presents a promise strategy of structure designing and composition optimization for 2D layered materials in advanced energy storage application.