A protocol was developed to fractionate soil particles down to the nanocolloid scale by combining sieving, sedimentation, centrifugation, and cross-flow filtration (CFF). The validity of the method and the performance of the CFF system were tested by characterizing fractions using laser granulometry, electron microscopy, and chemical analysis. The 0.1-lm-pore-size membrane CFF system effectively retained nanocolloids (\0.1 lm) as shown by laser granulometry and observed directly by transmission electron microscopy. However, environmental scanning electron microscopy images of freeze-dried colloids were very different from their TEM counterparts, suggesting that sample preparation influenced microscopy imaging. Chemical analysis of Cu, Cd, and organic carbon in each fraction showed that the concentrations of these components increased as particle size decreased, indicating colloids and nanocolloids play an important role in retaining trace metals. Particle-size fractionation combined with chemical analysis and electron microscopy can provide insight into the nature and properties of nanocolloids in soil.
The formation of severe dendritic sodium (Na) microstructure reduces the reversibility of anode and further hinders its practical implementation. In this work, an ionic‐electronic dual‐conducting (IEDC) scaffold composed of Na3P and carbon nanotubes is in situ developed by a scalable strategy with subsequent alloying reaction, for realizing dendrite‐free Na deposition under high current density and large areal capacity. The in situ formed Na3P with high sodiophilicity not only sets up a hierarchically efficient ionic conducting network, but also participates in the construction of reinforced solid electrolyte interphase, while carbon nanotubes can assemble an electronic conducting framework. As a result, the multifunctional IEDC scaffold contributes to smooth Na plating and exceptionally reversible Na stripping. High average Coulombic efficiency of 99.8% after prolonged 1200 cycles at 3 mA cm−2 and small overpotential of 20 mV over 250 h (equals to 530 cycles) at high rate of 5 mA cm−2 are obtained. The high availability of Na in IEDC scaffold enables the impressive performance of full cell with limited Na, using Na3V2(PO4)3 (NVP) cathode at practical level. More importantly, the as‐developed anode‐free full cell with IEDC||NVP configuration delivers a high capacity retention with long lifetime, indicating its great potential for practical Na metal batteries.
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