[en] Highlights: • The correlation between Li₂O₂ growth mechanism and O₂ adsorbability is established. • A strategy to realize a simultaneous large capacity and low overpotential is demonstrated. • The dominant role of the carbon additive on the discharge performance is revealed. Understanding and controlling the growth of the vital Li₂O₂ product, which is associated with intrinsic property of cathode surface, is essential to design effective cathode catalysts in Li-O₂ batteries. Herein we establish the correlation between the Li₂O₂ growth model and the O₂ adsorbability on cathode surface that determines the pathway of the first electron transfer to O₂. The weak O₂ adsorbability drives the solution growth model to form Li₂O₂ toroid, while the strong one drives the surface growth model to thin film. Based on this mechanism, we select the N-doped carbon nanocages as cathode to realize a simultaneous large discharge capacity and low charge overpotential by forming copious thin-film Li₂O₂, deriving from its high specific surface area and enhanced O₂ adsorbability due to N-doping. Our study demonstrates an effective strategy to design advanced cathode catalysts in Li–O₂ batteries and potentially other metal-air batteries.

[en] Highlights: • The electrocatalysis of N-doped sp² carbon for LiPS conversion is revealed by combined experimental and theoretical study. • The hNCNC unites the mutual-promoted functions of physical confinement, chemical adsorption and electrocatalysis together. • A record-high power performance and an excellent durability of Li-S batteries are achieved by using hNCNC. • The performance-structure correlation is well-established. -- Abstract: Lithium-sulfur batteries are facing the big challenge of high-rate charge/discharge with long durability owing to the severe shuttle and polarization effects. Herein, we report a durable high-power cathode for lithium-sulfur batteries by employing multifunctional hierarchical nitrogen-doped carbon nanocages (hNCNC) to encapsulate sulfur and serve as interlayer. The highly-efficient electrocatalytic function of nitrogen-doped sp²-carbon to lithium-polysulfides conversion reactions is revealed by electrocatalytic experiments and density functional theory simulations. The excellent catalytic and charge-transfer functions of hNCNC, together with its physical confinement and chemical adsorption to the polysulfides, effectively suppress the polarization and shuttle effects, leading to the high-power performance with a capacity of 539 mAh g⁻¹ at ultrahigh current density of 20 A g⁻¹ for the sulfur cathode with the areal loading of 0.8 mg cm⁻². The superb durability is demonstrated by 1000 cycles at 10 A g⁻¹ with a retained capacity of 438 mAh g⁻¹. When the areal sulfur loading is increased to 3 mg cm⁻², a high capacity of 605 mAh g⁻¹ is still obtained at the high current density of 3 A g⁻¹. This study provides an effective approach to durable high-power lithium-sulfur batteries by designing suitable electrocatalytic-active carbon-based hosts.

[en] Highlights: • Hydratable plastics is introduced as a new class of material for solar desalination for the first time. • A high evaporation rate of 3.01 kg m^–2 h^–1 under 1-sun irradiation intensity was achieved through enthalpy reduction. • Origins of the enthalpy reduction elucidated to be due to the formation of weaker hydroxyl-water hydrogen bonds. • An evaporation rate of 7.35 kg m^–2 h^–1 was achieved under 3-sun irradiation intensity through surface architectural design. In this work, hydratable plastics is being introduced as a new class of materials for effective solar desalination for the first time. In the form of highly amorphous regenerated cellulose, the 3D-printed material achieves a high evaporation rate of 3.01 kg m⁻² h⁻¹ under 1-sun irradiation through vaporisation enthalpy reduction. In addition, this work demonstrates that evaporation rate saturation at higher irradiation can be overcome by improving rehydration rate through architectural design via 3D-printing. As such, an unprecedented evaporation rate of 7.35 kg m⁻² h⁻¹ under concentrated 3-sun irradiation was achieved. More importantly, water molecules are found to be more locally ordered, leading to more hydrogen bonding in the hydrated cellulose than in bulk. It turns out that the weaker cellulose-water hydrogen bonds with longer bond length and higher deviation from non-linearity is the most probable origins for the significant reduction of vaporisation enthalpy. The 3D-printed evaporators also exhibits long-term stability and anti-salt-fouling ability in evaporating saline water due the interconnectivity of the micro and sub-nano water channels. Finally, purified water collected from a handmade device possess high drinkability.