Porous structured silicon has been regarded as a promising candidate to overcome pulverization of silicon-based anodes. However, poor mechanical strength of these porous particles has limited their volumetric energy density towards practical applications. Here we design and synthesize hierarchical carbon-nanotube@silicon@carbon microspheres with both high porosity and extraordinary mechanical strength (>200 MPa) and a low apparent particle expansion of ~40% upon full lithiation. The composite electrodes of carbon-nanotube@silicon@carbon-graphite with a practical loading (3 mAh cm⁻²) deliver ~750 mAh g⁻¹ specific capacity, <20% initial swelling at 100% state-of-charge, and ~92% capacity retention over 500 cycles. Calendered electrodes achieve ~980 mAh cm⁻³ volumetric capacity density and 92% capacity retention over 500 cycles. This work is a leap in silicon anode development and provides insights into the design of electrode materials for other batteries.

Engineering suitable redox molecules: In a flow battery, catholyte and anolyte are stored in separate tanks, and pumps are used to circulate the fluids into a stack with electrodes separated by a thin membrane. Such batteries are ideal for large-scale grid storage applications; however, suitable redox molecules are currently limited. Feng et al. used “molecular engineering” to modify an inexpensive precursor (9-fluorenone) as the basis for an organic-based redox flow battery (see the Perspective by Hu and Liu). The authors tested a series of variant molecules in a redox flow battery in which the reactions involve reversible ketone hydrogenation and dehydrogenation in an aqueous electrolyte. These reactions have advantageous features, including two-electron redox and operation in air and at elevated temperatures (50°C), that are more suitable for real-world applications. Science , abd9795, this issue p. 836 ; see also abi5911, p. 788

Magnetic carbon–iron nanoadsorbents fabricated by carbonizing cellulose and reducing Fe₃O₄ nanoparticles or Fe(NO₃)₃ (the products are denoted as MC–O and MC–N, respectively) have demonstrated great Cr(VI) removal. MC–N with a higher proportion of zero-valence iron (ZVI) and bigger specific surface area exhibited better resistance to oxygen and acid than MC–O due to its smaller pore size. The Cr(VI) removal was highly pH-dependent. For example, 4.0 mg L⁻¹ Cr(VI) neutral solution was completely purified by 2.5 g L⁻¹ MC–O and MC–N within 10 min. 1000 mg L⁻¹ Cr(VI) solution at pH 1.0 was completely removed by both nanoadsorbents in 10 min. The MC–O nanoadsorbents had a higher removal percentage (98.1%) than MC–N (93.5%) at pH 7.0, while MC–N had a removal capacity of 327.5 mg g⁻¹, much higher than 293.8 mg g⁻¹ of MC–O at pH 1.0. A chemical adsorption was revealed from the pseudo-second-order kinetic study. Monolayer adsorption of Cr(VI) was revealed by a better fitting of the Langmuir model isotherm, rather than multilayer adsorption for the Freundlich model. These nanoadsorbents could be easily separated from solution by using a permanent magnet after being treated with Cr(VI). Finally, the Cr(VI) removal mechanisms were proposed considering the Cr(VI) reduction and precipitation of Cr(III).