In lithium metal batteries, electrolytes containing a high concentration of salts have demonstrated promising cyclability, but their practicality with respect to the cost of materials is yet to be ...proved. Here we report a fluorinated aromatic compound, namely 1,2‐difluorobenzene, for use as a diluent solvent in the electrolyte to realize the “high‐concentration effect”. The low energy level of the lowest unoccupied molecular orbital (LUMO), weak binding affinity for lithium ions, and high fluorine‐donating power of 1,2‐difluorobenzene jointly give rise to the high‐concentration effect at a bulk salt concentration near 2 m, while modifying the composition of the solid‐electrolyte‐interphase (SEI) layer to be rich in lithium fluoride (LiF). The employment of triple salts to prevent corrosion of the aluminum current collector further improves cycling performance. This study offers a design principle for achieving a local high‐concentration effect with reasonably low bulk concentrations of salts.
1,2‐Difluorobenzene serves as an electrolyte diluent to realize the high‐concentration effect in lithium metal batteries even at a bulk salt concentration near 2 m. The incorporation of this diluent also induces an anion‐associated lithium solvation structure to passivate lithium metal with a LiF‐rich solid‐electrolyte‐interphase (SEI) layer, thereby resulting in superior cyclability.
This review focuses on newly emerging two-dimensional MXenes for gas sensing applications from a theoretical to an experimental view to guide future research. Various synthesis routes of 2D MXenes ...have been explored and recent success of various MXenes has allowed more knowledge on the relations between their structure and materials properties. We review distinctive gas sensing properties of MXenes in two aspects of theoretical and experimental view. Theoretical insight into the gas-surface interaction mechanism and experimental results of various MXenes on their sensing properties are complied and discussed. To tailor and enhance the sensing performance of MXenes, the parameters such as precursors, morphology, surface terminations, and interlayer structures are emphasized. Perspectives on challenges and opportunities are offered for further development of MXenes-based gas sensors.
Lithium metal anodes are steadily gaining more attention, as their superior specific capacities and low redox voltage can significantly increase the energy density of rechargeable batteries far ...beyond those of current Li‐ion batteries. Nonetheless, the relevant technology is still in a premature research stage mainly due to the uncontrolled growth of Li dendrites that ceaselessly cause unwanted side reactions with electrolyte. In order to circumvent this shortcoming, herein, an ionic liquid additive, namely, 1‐dodecyl‐1‐methylpyrrolidinium (Pyr1(12)+) bis(fluorosulfonyl)imide (FSI−), for conventional electrolyte solutions is reported. The Pyr1(12)+ cation with a long aliphatic chain mitigates dendrite growth via the combined effects of electrostatic shielding and lithiophobicity, whereas the FSI− anion can induce the formation of rigid solid–electrolyte interphase layers. The synergy between the cation and anion significantly improves cycling performance in asymmetric and symmetric control cells and a full cell paired with an LiFePO4 cathode. The present study provides a useful insight into the molecular engineering of electrolyte components by manipulating the charge and structures of the involved molecules.
An ionic liquid additive of 1‐dodecyl‐1‐methylpyrrolidinium (Pyr1(12)+) bis(fluorosulfonyl)imide (FSI‐) is reported for stable cycling of Li metal anodes. The Pyr1(12)+ cation with a long aliphatic chain engages an electrostatic shielding and lithiophobic effect, whereas the FSI‐ anion induces the formation of rigid solid–electrolyte interphase layers. The synergy between both ions suppresses dendrite growth and improves electrochemical performance significantly.
Two-dimensional (2D) nanomaterials have demonstrated great potential in the field of gas sensing due to their layered structures. Especially for 2D transition metal dichalcogenides (TMDs), inherent ...high surface areas and their unique semiconducting properties with tunable band gaps make them compelling for sensing applications. In combination with the general benefits of 2D nanomaterials, the incorporation of metal oxides into 2D TMDs is a recent approach for improving the gas sensing performance of these materials by the synergistic effects of the hybridization. This Review aims to comprehend the sensing mechanisms and the synergistic effects of various hybridizations of 2D TMDs and metal oxides. The Review begins with the gas sensing mechanisms and synthesis methods of 2D TMDs. Achievements in recent research on 2D TMDs and their metal oxide hybrids for sensor applications are then comprehensively compiled. To clearly understand the collective benefits of TMDs and metal oxide hybrids, the hybridization effects are discussed in three aspects: geometrical, electronic, and chemical effects.
In this paper, a design and control scheme of the inductive power transfer (IPT) system for electric vehicles are proposed, considering a wide variation in output voltage and coupling coefficient. ...The characteristics of the proposed IPT system and a design method for the resonant network are suggested. By utilizing the battery management converter at the secondary side, the design and control can be simplified while managing the output voltage and power of the battery. In order to achieve high efficiency by reducing the voltage-ampere rating, zero phase angle tracking control is proposed. In addition, a phase-shift control is applied to the primary side to ensure the stable system operation by limiting output voltage. A 3.3-kW laboratory prototype with magnetic power pads is manufactured, and the validity of the proposed design and control is verified through experimental results using the laboratory prototype.
Nonaqueous carbonate electrolytes are commonly used in commercial lithium‐ion battery (LIB). However, the sluggish Li+ diffusivity and high interfacial charge transfer resistance at low temperature ...(LT) limit their wide adoption among geographical areas with high latitudes and altitudes. Herein, a rational design of new electrolytes is demonstrated, which can significantly improve the low temperature performance below −20 °C. This electrolyte is achieved by tailoring the chemical structure, i.e., altering the fluorination position and the degree of fluorination, of ethyl acetate solvent. It is found that fluorination adjacent to the carbonyl group or high degree of fluorination leads to a stronger electron‐withdrawing effect, resulting in low atomic charge on the carbonyl oxygen solvating sites, and thus low binding energies with Li+ ions at LT. The optimal electrolyte 2,2,2‐trifluoroethyl acetate (EA‐f) shows significantly improved cycle life and C‐rate of a NMC622/graphite cell when cycled at −20 °C and −40 °C, respectively. In addition to superior LT performance, the electrolyte is nonflammable and tolerant for high voltage charging all owing to its fluorine content. This work provides guidance in designing next‐generation electrolytes to address the critical challenge at subzero temperatures.
A rational design of electrolytes for low temperature lithium‐ion batteries is presented. Fluorination adjacent to the carbonyl, or high degree of fluorination in ethyl acetate leads to stronger electron‐withdrawing effects, resulting in low atomic charge on the carbonyl oxygen solvating sites, and thus low binding energies with Li+ ions. NMC622/graphite cells using 2,2,2‐trifluoroethyl acetate show significantly improved low temperature performance.
Wearable gas sensors have received lots of attention for diagnostic and monitoring applications, and two-dimensional (2D) materials can provide a promising platform for fabricating gas sensors that ...can operate at room temperature. In the present study, the room temperature gas-sensing performance of Ti3C2T x nanosheets was investigated. 2D Ti3C2T x (MXene) sheets were synthesized by removal of Al atoms from Ti3AlC2 (MAX phases) and were integrated on flexible polyimide platforms with a simple solution casting method. The Ti3C2T x sensors successfully measured ethanol, methanol, acetone, and ammonia gas at room temperature and showed a p-type sensing behavior. The fabricated sensors showed their highest and lowest response toward ammonia and acetone gas, respectively. The limit of detection of acetone gas was theoretically calculated to be about 9.27 ppm, presenting better performance compared to other 2D material-based sensors. The sensing mechanism was proposed in terms of the interactions between the majority charge carriers of Ti3C2T x and gas species.
Due to the exceptional theoretical energy density and low cost of elemental sulfur, lithium–sulfur (Li–S) batteries are spotlighted as promising post‐lithium‐ion batteries. Despite these advantages, ...the performance of Li–S batteries would need to be improved further for their wide dissemination in practical applications. Here, cobalt(II)‐centered fluorinated phthalocyanine, namely, F‐Co(II)Pc, is reported as a multi‐functional component for sulfur cathodes with the following benefits: 1) enhanced conversion kinetics as a result of the catalytic effect of the cobalt(II) center, 2) efficient sulfur linkage via the fluorine functionality, which undergoes a nucleophilic aromatic substitution (SNAr) reaction, 3) suppression of the shuttling issue by the nitrogen atoms because of their strong affinity with polysulfides, and 4) the necessary aromaticity to engage in π–π interaction with reduced graphene oxide for electrical conductivity. The resulting electrode has promising electrochemical properties, such as sustainable cycling for 700 cycles and robust operation with a sulfur loading of 12 mgsulfur cm−2, unveiling the promising nature of phthalocyanine and its related molecular families for advanced Li–S batteries.
Cobalt(II)‐centered fluorinated phthalocyanine (F‐Co(II)Pc) is introduced as a multi‐functional component for sulfur electrodes in Li–S batteries. F‐Co(II)Pc improves the kinetics of the conversion reaction by utilizing the catalytic effect of cobalt(II), enables covalent linkage with elemental sulfur, mitigates the shuttling effect, and engages in π–π interaction with reduced graphene oxide, with the combined effect of robust cycling with a sulfur loading of 12 mgsulfur cm−2.
Background:The Korea Acute Myocardial Infarction Registry (KAMIR)-National Institutes of Health (NIH) registry has the aim of evaluating the clinical characteristics, management, and long-term ...outcomes of patients with acute myocardial infarction (AMI) in Korea.Methods and Results:Patients hospitalized for AMI in 20 tertiary university hospitals in Korea have been enrolled since November 2011. The study is expected to complete the scheduled enrollment of approximately 13,000 patients in October 2015, and follow-up duration is up to 5 years for each patient. As of October 2015, an interim analysis of 13,623 subjects was performed to understand the baseline clinical profiles of the study population. The mean age was 64.1 years; 73.5% were male; and 48.2% were diagnosed with ST-segment elevation AMI. Hypertension is a leading cause of AMI in Korea (51.2%), followed by smoking (38.5%) and diabetes mellitus (28.6%). Percutaneous coronary intervention was performed in 87.4% and its success rate was very high (99.4%). In-hospital, 1-year, and 2-year mortality rates were 3.9%, 4.3%, and 8.6%, respectively. The rates of major adverse cardiac events at 1 and 2 years were 9.6% and 18.8%, respectively.Conclusions:This analysis demonstrated the clinical characteristics of Korean AMI patients in comparison with those of other countries. It is necessary to develop guidelines for Asian populations to further improve their prognosis. (Circ J 2016; 80: 1427–1436)
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