Despite being recognized as a promising technique for treating high salinity water, membrane distillation (MD) has been plagued by the scaling of sparingly soluble salts. The growth of crystals can not only create additional resistance to evaporating water at the feed-membrane interface, but also alter the hydrophobic network to bridge the feed and distillate (i.e., result in the phenomenon of wetting). When recognizing the uncertain behaviors of calcium sulfate (CaSO 4 ) scaling in MD, this study was motivated to ascertain whether the crystal-membrane interactions could be dependent on the variation in crystalline morphology. In particular, optical coherence tomography (OCT) was employed to characterize the scaling-induced wetting via a direct-observation-through-the-membrane (DOTM) mode, which mitigated the effects of developing an external scaling layer on resolving the crystal-membrane interactions. The improved in-situ characterization suggests that the crystalline morphology of CaSO 4 could be effectively regulated by varying the stoichiometry of crystallizing ions; the richness of calcium in the aqueous environment for crystallization would be in favor of weakening the crystal-membrane interactions. The stoichiometry-dependent growth of CaSO 4 crystals can be exploited to develop an effective strategy for preventing the hydrophobic network from being wetted or irreversibly damaged.
Chengyuan Liu,Zhiwei Liu,Hongkun Niu,Cong Wang,Zhaowen Wang,Bingliang Gao,Jingjing Liu,Mark Taylor
We provide a method for preparation of binder-free cathode for rechargeable aluminum-ion batteries (AIBs). Ultrasonicated natural graphite (u-NG) flakes in N-methylpyrrolidone (NMP) is drop-casted to a carbon fiber cloth (CFC) to obtain binder-free u-GF@CFC cathode for AIBs. We also provide an in-situ Raman spectral technology and the corresponding in-situ Raman cell to determine the mechanism of intercalation/deintercalation reactions of the chloroaluminate ions at cathode of AIBs. The in-situ Raman spectra are recorded using a Raman spectrometer combined with a potentiostat/galvanostat model electrochemical workstation. • A simple preparation method of a binder-free u-GF@CFC cathode is suggested. • The u-GF@CFC cathode is obtained by drop-casting ultrasonicated graphite flakes on the surface and internal gaps of the carbon fiber cloth. • The method includes the in-situ Raman spectral technology and the corresponding in-situ Raman cell.
Shinuo Kang,Fushan Geng,Xiaobing Lou,Guozhong Lu,Yuxin Liao,Ming Shen,Bingwen Hu
The extreme fast charging (XFC) capability of graphite anodes is becoming increasingly important with the development of electric vehicles due to the usage and safety requirement. In this work, the XFC performance of the graphite anodes is improved by simply adding fluoroethylene carbonate (FEC) into the electrolyte. This robust system is studied by in situ nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) experiments to unravel the kinetic mechanism. The Li local environments in the graphite are detected by in situ NMR, which reveals the phase transitions during XFC without and with the FEC additive and the corresponding Li-ion mobility. The graphite conductivity variation is estimated by in situ EPR, and the plated Li can be clearly observed in the later period of XFC. The kinetics of graphite lithiation is deduced to be surface-controlled during the dilute stages and bulk-controlled during the dense stages. The solid electrolyte interphase (SEI) formed with FEC is more homogeneous and richer in LiF, which delivers a faster Li+ transport ability and results in the improvement of the surface kinetics. The major advantage of FEC additive is in the optimization of the Li plating behavior. Without FEC, the Li deposits grow locally, while the FEC additive consumes more currents to form the SEI and facilitate the uniform deposition of metallic Li on graphite during XFC. These results display the versatility of in situ NMR and EPR technologies in the research of XFC kinetics.
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