Rechargeable batteries paired with sodium (Na)-metal anodes are considered as one of the most promising high energy and low-cost energy storage systems. However, the use of highly reactive Na metal and the formation of Na dendrites during battery operation have caused signi cant safety concerns, especially when highly ammable liquid electrolytes are used. Herein, we design and develop a solventfree solid polymer electrolytes (SPEs) based on a per uoropolyether (PFPE) terminated polyethylene glycol (PEG)-based block copolymer for safe and stable all-solid-state Na-metal batteries. Compared with traditional poly(ethylene oxide) (PEO) or PEG SPEs, our results suggest that block copolymer design allows for the formation of self-assembled microstructures leading to high storage modulus at elevated temperatures with the PEG domains providing transport channels even at high salt concentration (EO/Na + = 8:2). Moreover, it is demonstrated that the incorporation of PFPE segments enhances the Na + transference number of the electrolyte to 0.46 at 80 o C. Finally, the proposed SPE exhibits highly stable symmetric cell cycling performance with high current density (0.5 mA cm -2 and 1.0 mAh cm -2 , up to 1300 hours). The assembled all-solid-state Na-metal batteries with Na 3 V 2 (PO 4 ) 3 cathode demonstrate outstanding rate performance, high capacity retention and long-term charge/discharge stability (CE = 99.91%) after more than 900 cycles.

Ionic liquid electrolytes have been utilized in rechargeable batteries, yet their effect on the anode interphase evolution has been barely studied. Herein, we investigate the interfacial characteristics of carbon anodes in sodium-ion batteries (NIBs) in contact with superconcentrated sodium bis(fluoromethane)sulfonimide (NaFSI)/N-methyl-N-propylpyrrolidinium bis(fluoromethane) sulfonimide (C 3 mpyrFSI). A long cycle life of the cell, up to 3500 cycles with 320 mAh/g, is achieved, which is contributed by the anion-derived inorganic solid electrolyte interphase (SEI) layer on the anode. Comparison is made with a traditional carbonate electrolyte using the same sodium salt (1 M NaFSI in EC/DMC), showing that the latter results in a thick organic-dominant SEI layer from decomposition of the organic solvents. Here we correlate the influence of the anion decomposition species in the IL electrolyte with high ionic conductivity, and accelerated Na desolvation and faster diffusion kinetics, giving some fundamental insights into interfacial phenomena in NIBs.

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In this paper, biochar derived from poplar catkins was used as an economical and renewable adsorbent for adsorption organic and inorganic pollutants such as, dyes, organic compounds, and heavy metal ions from wastewater. Mesoporous activated carbonized poplar catkins (ACPCs) were produced from char as a by-product by carbonized poplar catkins (CPCs). With their high surface area, ACPCs exhibited the maximum adsorption capacities of 71.85 and 110.17 mg/g for the removal of inorganic U(VI) and Co(II). Compared other biochars adsorbents, ACPCs can also adsorb organic pollutants with the maximum adsorption capacities of 534, 154, 350, 148 and 384 mg/g for methylene blue (MB), methyl orange (MO), Congo red (CR), chloramphenicol (CAP) and naphthalene. The adsorption of organic pollutants was fitted with pseudo-first order, pseudo-second order, and intra-particle diffusion kinetic models figure out the kinetic parameters and adsorption mechanisms. Langmuir adsorption isotherm was found to be suitable for Co(II) and U(VI) adsorption and thermodynamic studies indicated adsorption processes to be endothermic and spontaneous. The adsorption process includes both outer-sphere surface complexes and hydrogen-bonding interactions. The results showed that biochar derived from poplar catkins was a potential material to remove pollutants in wastewater.

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Optical breakdown by ultrashort laser pulses in dielectrics presents an efficient method to deposit laser energy into materials that otherwise exhibit minimal absorption at low laser intensities. During optical breakdown, a high density of free electrons is formed in the material, which dominates energy absorption, and, in turn, the material removal rate during ultrafast laser-material processing. Classical models assume a spatially uniform electron population and constant laser intensity in the focal region, which results in time-dependent expressions only, i.e., the rate equations, to predict electron evolution induced by nanosecond and picosecond pulses. For femtosecond pulses, however, the small spatial extent of the pulse requires that the pulse propagation be considered, which results in an inhomogeneous plasma and localized electron formation during optical breakdown. In this work, a femtosecond breakdown model is combined with the classical rate equations to determine both time- and position-dependent electron density during femtosecond optical breakdown in water. The model exhibits good agreement when compared with experimental results. For other transparent or moderately absorbing dielectric media, the model also shows promise for determining the time- and position-dependent electron evolution induced by ultrashort laser pulses. Another interesting result is that the maximum electron density formed during femtosecond-laser-induced optical breakdown may exceed the conventional limit imposed by the plasma frequency.

We have investigated the sodium electrochemistry and the evolution and chemistry of the solid–electrolyte interphase (SEI) upon cycling Na metal electrodes in two ionic liquid (IL) electrolytes. The effect of the IL cation chemistry was determined by examining the behavior of a phosphonium IL (P111i4FSI) in comparison to its pyrrolidinium-based counterpart (C3mpyrFSI) at near-saturated NaFSI salt concentrations (superconcentrated ILs) in their dry state and with water additive. The differences in their physical properties are reported, with the P111i4FSI system having a lower viscosity, higher conductivity, and higher ionicity in comparison to the C3mpyrFSI-based electrolyte, although the addition of 1000 ppm (0.1 wt %) of water had a more dramatic effect on these properties in the latter case. Despite these differences, there was little effect in the ability to sustain stable cycling at moderate current densities and capacities (being nearly identical at 1 mA cm–2 and 1 mAh cm–2). However, the IL based on the phosphonium cation is shown to support more demanding cycling with high stability (up to 4 mAh cm–2 at 1, 2, and 4 mA cm–2 current density), whereas C3mpyrFSI rapidly failed (at 1 mA cm–2 /4 mAh cm–2). The SEI was characterized ex situ using solid-state 23Na NMR, XPS, and SEM and showed that the presence of a Na complex, identified in our previous work on C3mpyrFSI to correlate with stable, dendrite-free Na metal cycling, was also more prominent and coexisted with a NaF-rich surface. The results here represent a significant breakthrough in the development of high-capacity Na metal anodes, clearly demonstrating the superior performance and stability of the P111i4FSI electrolyte, even after the addition of water (up to 1000 ppm (0.1 wt %)), and show great promise to enable future higher-temperature (50 °C) Na-metal-based batteries.

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