A strategy called ultramicroporous building unit (UBU) is introduced. It allows the creation of hierarchical bi‐porous features that work in tandem to enhance gas uptake capacity and separation. ...Smaller pores from UBUs promote selectivity, while larger inter‐UBU packing pores increase uptake capacity. The effectiveness of this UBU strategy is shown with a cobalt MOF (denoted SNNU‐45) in which octahedral cages with 4.5 Å pore size serve as UBUs. The C2H2 uptake capacity at 1 atm reaches 193.0 cm3 g−1 (8.6 mmol g−1) at 273 K and 134.0 cm3 g−1 (6.0 mmol g−1) at 298 K. Such high uptake capacity is accompanied by a high C2H2/CO2 selectivity of up to 8.5 at 298 K. Dynamic breakthrough studies at room temperature and 1 atm show a C2H2/CO2 breakthrough time up to 79 min g−1, among top‐performing MOFs. Grand canonical Monte Carlo simulations agree that ultrahigh C2H2/CO2 selectivity is mainly from UBU ultramicropores, while packing pores promote C2H2 uptake capacity.
Hole to differentiate, and hole to accommodate. Two types of pores can mingle together using a strategy called UBU (ultramicroporous building unit). This strategy results in a promising gas absorbent for excellent C2H2 storage capacity and top‐level C2H2/CO2 separation ability.
Recently, a novel 4
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Einstein–Gauss–Bonnet gravity was formulated by Glavan and Lin (Phys Rev Lett 124(8):081301, 2020). Although whether the theory is well defined is currently debatable, the ...spherically symmetric black hole solution is still meaningful and worthy of study. In this paper, we study the geodesic motions in the spacetime of the spherically symmetric black hole solution. First of all, we find that a negative GB coupling constant is allowable, as in which case the singular behavior of the black hole can be hidden inside the event horizon. Then we calculate the innermost stable circular orbits for massive particles, which turn out to be monotonic decreasing functions of the GB coupling constant. Furthermore, we study the unstable photon sphere and shadow of the black hole. It is interesting to find that the proposed universal bounds on black hole size in Lu and Lyu (Phys Rev D 101(4):044059, 2020) recently can be broken when the GB coupling constant takes a negative value.
Electrical devices generate heat at work. The heat should be transferred away immediately by a thermal manager to keep proper functions, especially for high‐frequency apparatuses. Besides high ...thermal conductivity (K), the thermal manager material requires good foldability for the next generation flexible electronics. Unfortunately, metals have satisfactory ductility but inferior K (≤429 W m−1 K−1), and highly thermal‐conductive nonmetallic materials are generally brittle. Therefore, fabricating a foldable macroscopic material with a prominent K is still under challenge. This study solves the problem by folding atomic thin graphene into microfolds. The debris‐free giant graphene sheets endow graphene film (GF) with a high K of 1940 ± 113 W m−1 K−1. Simultaneously, the microfolds render GF superflexible with a high fracture elongation up to 16%, enabling it more than 6000 cycles of ultimate folding. The large‐area multifunctional GFs can be easily integrated into high‐power flexible devices for highly efficient thermal management.
An atomic crystal‐folding principle is proposed for designing highly thermal‐conductive yet superflexible graphene film. Debris‐free, giant graphene sheets and folded atomic thin crystals afford macroscopic assembled graphene film a high thermal conductivity 1940 W m−1 K−1 and fracture elongation 16%, respectively. This principle opens the door for high‐performance yet flexible inorganic/ceramic macroscopic materials and devices.
The lifespan of practical lithium (Li)‐metal batteries is severely hindered by the instability of Li‐metal anodes. Fluorinated solid electrolyte interphase (SEI) emerges as a promising strategy to ...improve the stability of Li‐metal anodes. The rational design of fluorinated molecules is pivotal to construct fluorinated SEI. Herein, design principles of fluorinated molecules are proposed. Fluoroalkyl (−CF2CF2−) is selected as an enriched F reservoir and the defluorination of the C−F bond is driven by leaving groups on β‐sites. An activated fluoroalkyl molecule (AFA), 2,2,3,3‐tetrafluorobutane‐1,4‐diol dinitrate is unprecedentedly proposed to render fast and complete defluorination and generate uniform fluorinated SEI on Li‐metal anodes. In Li–sulfur (Li−S) batteries under practical conditions, the fluorinated SEI constructed by AFA undergoes 183 cycles, which is three times the SEI formed by LiNO3. Furthermore, a Li−S pouch cell of 360 Wh kg−1 delivers 25 cycles with AFA. This work demonstrates rational molecular design principles of fluorinated molecules to construct fluorinated SEI for practical Li‐metal batteries.
Design principles of fluorinated molecules were proposed to construct a fluorinated solid electrolyte interphase for practical lithium‐metal batteries.
Lithium–sulfur (Li–S) batteries promise great potential as high‐energy‐density energy‐storage devices due to their ultrahigh theoretical energy density of 2600 Wh kg−1. Evaluation and analysis on ...practical Li–S pouch cells are essential for achieving actual high energy density under working conditions and affording developing directions for practical applications. This review aims to afford a comprehensive overview of high‐energy‐density Li–S pouch cells regarding 7 years of development and to point out further research directions. Key design parameters to achieve actual high energy density are addressed first, to define the research boundaries distinguished from coin‐cell‐level evaluation. Systematic analysis of the published literature and cutting‐edge performances is then conducted to demonstrate the achieved progress and the gap toward practical applications. Following that, failure analysis as well as promotion strategies at the pouch cell level are, respectively, discussed to reveal the unique working and failure mechanism that shall be accordingly addressed. Finally, perspectives toward high‐performance Li–S pouch cells are presented regarding the challenges and opportunities of this field.
High‐energy‐density lithium–sulfur pouch cells are cpomprehensively reviewed regarding the key design parameters, the current performances, and recent advances on failure analysis and promotion strategies on cathode, electrolyte, and anode.
Perovskite light‐emitting diodes (PeLEDs) show great application potential in high‐quality flat‐panel displays and solid‐state lighting due to their steadily improved efficiency, tunable colors, ...narrow emission peak, and easy solution‐processing capability. However, because of high optical confinement and nonradiative charge recombination during electron–photon conversion, the highest reported efficiency of PeLEDs remains far behind that of their conventional counterparts, such as inorganic LEDs, organic LEDs, and quantum‐dot LEDs. Here a facile route is demonstrated by adopting bioinspired moth‐eye nanostructures at the front electrode/perovskite interface to enhance the outcoupling efficiency of waveguided light in PeLEDs. As a result, the maximum external quantum efficiency and current efficiency of the modified cesium lead bromide (CsPbBr3) green‐emitting PeLEDs are improved to 20.3% and 61.9 cd A−1, while retaining spectral and angular independence. Further reducing light loss in the substrate mode using a half‐ball lens, efficiencies of 28.2% and 88.7 cd A−1 are achieved, which represent the highest values reported to date for PeLEDs. These results represent a substantial step toward achieving practical applications of PeLEDs.
Highly efficient perovskite light‐emitting diodes are achieved by implementing a simple and cost‐effective method for efficient outcoupling of waveguided light. A record external quantum efficiency of 28.2% is realized for the device based on cesium lead bromide (CsPbBr3), while retaining the same spectral response for broad viewing angles.
The influence of land use patterns on stream water quality is scale-dependent in space and time. Understanding the relationship between landscape characteristics and water quality is of great ...importance to improve water contamination prediction in unmonitored watersheds and for providing guidelines for watershed land use planning. In this study, five water sampling sites in the upper Dan River basin were established to monitor seasonal water chemical contamination over the period of 2000 to 2008. The relationships between land use patterns and water quality were analyzed across multiple-scales using redundancy analysis. The results showed that stream water quality variables displayed highly temporal variations, with electrical conductivity (EC), ammonium nitrogen (NH4+-N), nitrate nitrogen (NO3−N), and total suspended solids (TSS) all generally displaying higher levels in the wet season, while there were higher concentrations of biochemical oxygen demand (BOD5), chemical oxygen demand (CODcr), and dissolved oxygen (DO) in the dry season. The total contribution of land use patterns on overall water quality was stronger at the riparian scale than at the catchment and reach scales during the wet season. However, different land use metrics had different scale effects. Urban land had a higher positive relationship with degraded water quality at small scales than at large scales, whereas agricultural land displayed the opposite scale effects. Forest and grassland explained more water quality variations at the riparian scale than at other scales. Analyses of spatial development patterns suggested that size, density, aggregation, and diversity of landscape patterns were important factors impacting on stream water quality. The results provide important information regarding sustainable land use and landscape planning at multiple-scales that can be used to improve water quality.
•Influence of land use patterns on water quality is scale-dependent.•Water quality is generally linked to land uses at riparian scale.•Land uses had strong relationship with water quality during wet season.•Land use planning was suggested at multiple-scales to improve water quality.
Stable operation at elevated temperature is necessary for lithium metal anode. However, Li metal anode generally has poor performance and safety concerns at high temperature (>55 °C) owing to the ...thermal instability of the electrolyte and solid electrolyte interphase in a routine liquid electrolyte. Herein a Li metal anode working at an elevated temperature (90 °C) is demonstrated in a thermotolerant electrolyte. In a Li|LiFePO4 battery working at 90 °C, the anode undergoes 100 cycles compared with 10 cycles in a practical carbonate electrolyte. During the formation of the solid electrolyte interphase, independent and incomplete decomposition of Li salts and solvents aggravate. Some unstable intermediates emerge at 90 °C, degenerating the uniformity of Li deposition. This work not only demonstrates a working Li metal anode at 90 °C, but also provides fundamental understanding of solid electrolyte interphase and Li deposition at elevated temperature for rechargeable batteries.
A Li metal anode working at 90 °C is demonstrated in a thermotolerant liquid electrolyte. The anode undergoes 100 cycles in a Li|LiFePO4 battery at 90 °C (10 cycles in a practical carbonate electrolyte). High operation temperature promotes independent and incomplete decomposition of Li salts and solvents to form a distinctive solid electrolyte interphase.
Glycine, proline, and hydroxyproline (Hyp) contribute to 57% of total amino acids (AAs) in collagen, which accounts for one-third of proteins in animals. As the most abundant protein in the body, ...collagen is essential to maintain the normal structure and strength of connective tissue, such as bones, skin, cartilage, and blood vessels. Mammals, birds, and fish can synthesize: (1) glycine from threonine, serine, choline, and Hyp; (2) proline from arginine; and (3) Hyp from proline residues in collagen, in a cell- and tissue-specific manner. In addition, livestock (e.g., pigs, cattle, and sheep) produces proline from glutamine and glutamate in the small intestine, but this pathway is absent from birds and possibly most fish species. Results of the recent studies indicate that endogenous synthesis of glycine, proline, and Hyp is inadequate for maximal growth, collagen production, or feed efficiency in pigs, chickens, and fish. Although glycine, proline and Hyp, and gelatin can be used as feed additives in animal diets, these ingredients except for glycine are relatively expensive, which precludes their inclusion in practical rations. Alternatively, hydrolyzed feather meal (HFM), which contains 9% glycine, 5% Hyp, and 12% proline, holds great promise as a low cost but abundant dietary source of glycine, Hyp, and proline for ruminants and nonruminants. Because HFM is deficient in most AAs, future research efforts should be directed at improving the bioavailability of its AAs and the balance of AAs in HFM-supplemented diets. Finally, HFM may be used as a feed additive to prevent or ameliorate connective tissue disorders in domestic and aquatic animals.
The lifespan of high‐energy‐density lithium metal batteries (LMBs) is hindered by heterogeneous solid electrolyte interphase (SEI). The rational design of electrolytes is strongly considered to ...obtain uniform SEI in working batteries. Herein, a modification of nitrate ion (NO3−) is proposed and validated to improve the homogeneity of the SEI in practical LMBs. NO3− is connected to an ether‐based moiety to form isosorbide dinitrate (ISDN) to break the resonance structure of NO3− and improve the reducibility. The decomposition of non‐resonant −NO3 in ISDN enriches SEI with abundant LiNxOy and induces uniform lithium deposition. Lithium–sulfur batteries with ISDN additives deliver a capacity retention of 83.7 % for 100 cycles compared with rapid decay with LiNO3 after 55 cycles. Moreover, lithium–sulfur pouch cells with ISDN additives provide a specific energy of 319 Wh kg−1 and undergo 20 cycles. This work provides a realistic reference in designing additives to modify the SEI for stabilizing LMBs.
The modification of NO3− is achieved by connecting NO3− to an ether‐based moiety. The broken resonance structure of −NO3 improves its reducibility compared with NO3−. The decomposition of −NO3 forms a LiNxOy‐rich solid electrolyte interphase (SEI) and induces uniform Li deposition.
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