Metallic lithium (Li) has been considered as an attractive anode material for next-generation rechargeable batteries, owing to its high theoretical capacity (3860 mAh g -1 ), low redox potential (−3.040 V vs standard hydrogen electrode), and low density (0.59 g cm -3 ). [4][5] Nevertheless, the high activity of Li metal, nonuniform Li plating, large volume change, and the formation of fragile solid electrolyte interphase (SEI) layer in lithium metal batteries (LMBs) inevitably lead to negative effects of the low Coulombic efficiency (CE), the uncontrollable growth of Li dendrite, the formation of "dead" Li, etc. [6][7][8][9] These intractable problems can cause irreversible loss of Li metal and electrolyte, resulting in a sustaining capacity attenuation or even triggering thermal runaway and explosion of the battery. Thermal runaway-induced accidents should be a wakeup call that people need to focus more attention on the battery safety and avoid undesirable energy release during battery cycling, since the batteries with higher energy density always endure lower thermal stability during operation. [10][11][12] Consequently, it is of vital importance to achieve robust LMBs security in the progress of developing Li metal anode and constantly breaking the bottleneck of energy density.As a critical component in batteries, separator not only provides paths for Li ion transfer, but also prevents accidental contact of anode and cathode. [13] According to statistics, at least 90% of various battery abuses (e.g., mechanical-abuse, electrical-abuse, thermal-abuse, and electrochemical-abuse) are related to internal short circuits caused by the failure of separator. [14] The prominent weak point of conventional polyolefin separators is their low melting point (135 °C for polyethylene (PE) separator and 165 °C for polypropylene (PP) separator), [15] which means they can easily shrink and collapse upon thermalabuse. To address this issue, tremendous efforts have been devoted to designing thermal-safety separators. [16] Metal oxides with polar surfaces (e.g., SiO 2 and Al 2 O 3 ) have been commonly reported as protective layers to enhance the thermal resistance of polyolefin separator. [17] Some inorganic materials with high Li-ion, thermal conductivity or flame retardance (e.g.,

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Gels prepared with the solvent-triggering method are attractive for their easy and fast preparation; however, the role of solvents in this process remains unclear, which hinders the efficient and accurate control of desired gel properties. In this study, the role of solvents in the solvent-triggering gelation process is studied using 9-fluorenylmethoxycarbonyl (Fmoc)-protected diphenylalanine (Fmoc-FF) as the gelator. Density functional theory (DFT)-based calculations and corresponding wavefunction analyses are conducted to identify the H-bonding interaction sites between the molecules. The calculation results clearly annotate the activating role of DMF and the triggering role of H 2 O in the gelation process. The solvation of Fmoc-FF by DMF can activate the Hbonding sites on the peptide chain, showing a conformation reversal and higher electrostatic potentials. Then, the H-bonding between Fmoc-FF and H 2 O is facilitated to trigger gelation. The physical Fmoc-FF/DMF/H 2 O gels show easily tuned mechanical strengths (G′ of 10 2 −10 5 Pa), injectable potentials (general yield strain < 100%), and stable recoverability (80−98% within 100 s). The regulation of these properties depends on not only the gelator concentration but also the H-bonding interactions with solvent molecules, which have seldom been studied in detail before. By understanding the effect of solvents, low-molecular-weight gelatorbased gels can be designed, prepared, and tuned efficiently for potential applications.

Tunnel fire is a major research topic in tunnel safety. Because of the tunnel's narrow and enclosed structure, smoke movement plays an important role in the investigation of the tunnel fire. In this paper, the Froude similarity principle is used to study the variation rule of the smoke back-layering length of tunnel ceiling jet induced by strong fire plume with different heat release rates, longitudinal ventilation velocities, and effective heights of fire source analyzed. It is found that the smoke back-layering length of tunnel ceiling jet induced by strong fire plume increases with the increase of effective height of fire source and decreases with the increase of longitudinal ventilation velocity. When the heat release rate is relatively small (Q < 60kW), the smoke back-layering length of the tunnel ceiling jet induced by strong fire plume increases as the heat release rate increases. However, for the larger heat release rate (Q ≥ 60kW), the smoke back-layering length of the tunnel ceiling jet induced by strong fire plume is mainly related to the longitudinal ventilation velocity. Based on Thomas's model and Li's model, by introducing the correction coefficient, correction formulas of the smoke back-layering length of tunnel ceiling jet induced by strong fire plume changing with the effective height of fire source are proposed.

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