Hard carbon is regarded as the most promising anode material for commercialization of Na ion batteries because of its high capacity and low cost. At present, the practical utilization of hard carbon anodes is largely limited by the low initial Coulombic efficiency (ICE). Na ions have been found to adopt an adsorption–insertion storage mechanism. In this paper a systematic way to control the defect concentration and porosity of hard carbon with similar overall architectures is shown. This study elucidates that the defects in the graphite layers are directly related to the ICE as they would trap Na ions and create a repulsive electric field for other Na ions so as to shorten the low‐voltage intercalation capacity. The obtained low defect and porosity hard carbon electrode has achieved the highest ICE of 86.1% (94.5% for pure hard carbon material by subtracting that of the conductive carbon black), reversible capacity of 361 mA h g−1, and excellent cycle stability (93.4% of capacity retention over 100 cycles). This result sheds light on feasible design principles for high performance Na storage hard carbon: suitable carbon layer distance and defect free graphitic layers.

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SnS–C nanocomposite can deliver a high capacity (568 mA h g−1) for Na storage based on the conversion and alloying reaction.

Hard carbon is considered as one of the most promising anodes in sodium-ion batteries due to its high capacity, low cost, and abundant resources. However, the available capacity and low initial Coulombic efficiency (ICE) limits the practical application of hard carbon anode. This issue results from the unclear understanding of the Na storage mechanism in hard carbon. In this work, a series of hard carbons with different microstructures are synthesized through an "up to down" approach by using a simple ball-milling method to illustrate the sodium-ion storage mechanism. The results demonstrate that ball-milled hard carbon with more defects and smaller microcrystalline size shows less low-potential-plateau capacity and lower ICE, which provides further evidence to the "adsorption-insertion" mechanism. This work might give a new perspective to design hard carbon material with a proper structure for efficient sodium-ion storage to develop high-performance sodium-ion batteries.

Pitaya-like Sb@C microspheres are prepared successfullyviaa facile aerosol spray drying method, which present a high initial capacity, good capacity retention and high rate capability for Na-ion storage. Morphological evolution reveals that the maintenance of the pitaya-like configuration guarantees excellent electrochemical performance.

Triclosan (TCS) and triclocarban (TCC) are widely used as bactericides in personal-care products. They are frequently found in environmental water and have the potential to cause a number of environmental and human health problems. In this study, we investigated adsorption and magnetic extraction for efficient removal of TCS and TCC from water and serum samples by core–shell structured magnetic covalent organic framework nanocomposites (Fe3O4@COFs). The as-prepared Fe3O4@COFs was fabricated on the Fe3O4 nanoparticles in situ growth strategy at room temperature via condensation reaction of 1,3,5-tris­(4-aminophenyl) benzene (TAPB) and terephthaldicarbox-aldehyde (TPA) in the presence of dimethyl sulfoxide (DMSO). The whole process of adsorption was monitored by ultrahigh performance liquid chromatography–tandem mass spectrometry (UHPLC-MS/MS) analysis with high sensitivity. The adsorption behaviors showed high adsorption capacity and fast adsorption. Furthermore, the adsorption performance through Langmuir and Freundlich isotherms showed multilayer adsorption through the interactions of space embedding effect, van der Waals forces, and benzene ring π–π stacking at a low concentration range and monolayer adsorption through strong π–π stacking at a high concentration range between the interface of TCS or TCC and Fe3O4@COFs at a high concentration range. Results indicated that the adsorption of TCS and TCC onto Fe3O4@COFs can be better represented by the pseudo-second-order model. Good removal efficiencies (82.3∼95.4%) and recoveries (92.9∼109.5%) of TCS and TCC in fetal bovine serum (FBS) and reusability at least 10 times were achieved. The Fe3O4@COFs exhibited high stability and excellent performance for the removal of TCS and TCC from water and biological samples. The results presented here thus reveal the exceptional potential of COFs for high-efficient environmental remediation.

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