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The stability of high‐energy‐density lithium metal batteries (LMBs) heavily relies on the composition of the solid electrolyte interphase (SEI) formed on lithium metal anodes. In this study, the inorganic‐rich SEI layer was achieved by incorporating bisalts additives into carbonate‐based electrolytes. Within this SEI layer, the presence of LiF, polythionate, and Li3N was observed, generated by combining 1.0 м lithium bis(trifluoromethanesulfonyl)imide in ethylene carbonate: ethyl methyl carbonate:dimethyl carbonate in a 1 : 1 : 1 volume ratio, with the addition of 2 wt% lithium difluorophosphate and 2 wt% lithium difluoro(oxalato)borate additives (EL‐DO). Furthermore, this formulation effectively mitigated corrosion of aluminum current collectors. EL‐DO exhibited outstanding performance, including an average coulombic efficiency of 98.2 % in Li||Cu cells and a stable discharge capacity of approximately 162 mAh g−1 after 200 cycles in a Li||LiNi0.8Co0.1Mn0.1O2 (NCM811) configuration. Moreover, EL‐DO displayed the potential to enhance the performance not only of LMBs but also of lithium‐ion batteries. In the case of Gr||NCM811 cell using EL‐DO, it consistently maintained high discharge capacities, even achieving around 135 mAh g−1 after the 100th cycle, surpassing the performance of other electrolytes. This study underscores the synergistic impact of bisalts additives in elevating the performance of lithium batteries. [ABSTRACT FROM AUTHOR]

Lithium metal batteries (LMBs) have the potential to significantly increase the energy density of advanced batteries in the future. Nonetheless, the dendritic lithium structures and low Coulombic efficiency (CE) of LMBs currently impede their applied implementation. Herein, a sulfite‐based electrolyte (SBE/FEC), including 1.0 m lithium bis(fluorosulfonyl)imide in a blend of ethylene sulfite and diethyl sulfite, and 5 wt% fluoroethylene carbonate is proposed. SBE/FEC is a highly efficient inhibitor against the growth of lithium dendrites through the formation of robust solid electrolyte interphase (SEI) layer. Raman spectroscopy and theoretical calculation indicate that in SBE/FEC, a significant portion of FSI− exists in associated complexes, playing a vital role in the creation of LiF‐rich passivation. Besides, the sulfite solvents decompose and yield polysulfide complexes in the SEI layer. A direct correlation between the proportion of cation–anion complexes and the contact angle between electrolyte and separator is elucidated through molecular dynamics simulations. The SBE/FEC system exhibits high CEs (98.3%) with Li||Cu cells, along with a steady discharge capacity of ≈137 mA h g−1 in Li||LiFePO4 cell. This study presents an effective approach for enhancing LMBs with sulfite‐based electrolytes, which can lead to high‐energy‐density next‐generation rechargeable batteries. [ABSTRACT FROM AUTHOR]

The successful implementation of supercapacitors in large‐scale applications necessitates careful consideration of safety aspects, along with factors such as energy density, power density, working voltage, and cycling performance. One effective method for ensuring safety is the utilization of nonflammable trimethyl phosphate (TMP) electrolyte in supercapacitors. However, this approach suffers from the drawback of low power density due to its low ionic conductivity. To overcome this limitation, we propose the addition of co‐solvents, namely propylene carbonate, acetonitrile, and propionitrile (PN), to enhance limited electrochemical properties of TMP‐based electrolytes. We systematically investigate the impact of incorporating TMP into various organic solvents on physical and electrochemical properties. Binary electrolytes show improved ionic conductivity, capacitance, power density, energy density, and working voltage compared to the single TMP‐based electrolyte. Notably, our result highlights that the carbon‐based supercapacitors using TMP‐PN with 70 : 30 volume ratio electrolyte provide the best compromise between ionic conductivity (13.5 mS cm−1), capacitance (24.0 F g−1), energy density (13.2 Wh kg−1), power density (2.3 kW kg−1), working voltage (3.5 V), and safety. By combining the nonflammable properties of TMP with co‐solvents, we can overcome the trade‐off between safety and electrochemical performances, presenting advancement in the development of supercapacitors for energy storage applications. [ABSTRACT FROM AUTHOR]

The formation of lithium (Li) dendrites and deterioration of the mechanical integrity of Nickel (Ni)‐rich cathodes directly hinder the commercialization of high‐voltage Li metal batteries (LMBs) with Ni‐rich cathodes. Herein, a novel electrolyte was tailored by combining non‐flammable triethyl phosphate (TEP) solvent with easily‐synthesized lithium nitrate (LiNO3) as the main salt and fluoroethylene carbonate (FEC) additive. The preferential electrochemical decomposition of LiNO3 and FEC provides robust and conductive solid/cathode electrolyte interphase (SEI/CEI) layer on the surface of the anode/cathode, which can protect both electrodes effectively during long‐term cycling. Benefiting from the synergetic effect of LiNO3 and FEC, NFE−LiNO3 exhibited outstanding performances in the cells with LiNi0.6Mn0.2Co0.2O2 (Li||NMC622) under high voltage (4.3 V), achieving an extremely high average efficiency of ∼100 % with an exceptional capacity retention of 90 % after 250 cycles. This study provides useful insights into the rational design of highly efficient, non‐flammable, and low‐cost electrolyte for long‐lasting high‐voltage LMBs. [ABSTRACT FROM AUTHOR]

Inverted type perovskite solar cells (PSCs) have recently emerged as a major focus in academic and industrial photovoltaic research. Their multiple advantages over conventional PSCs include easy processing, hysteresis‐free behavior, high stability, and compatibility for tandem applications. However, the maximum power conversion efficiency (PCE) of inverted PSCs still lags behind those of conventional PSCs because suitable charge‐selective materials for inverted PSCs are limited. In this study, excellent hole‐selective materials for inverted PSCs are introduced. A series of tricyclic aromatic rings containing O, S, or Se, respectively, as a core heteroatom, along with a phosphonic acid anchor, form a self‐assembled monolayer (SAM) that directly contacts the perovskite absorber. The influence of heteroatoms in the aromatic structure on the molecular energetics and operating characteristics of the corresponding inverted PSCs is investigated using complementary experimental techniques as well as density functional theory (DFT) calculations. It is found that all of the SAMs formed an energetically well‐aligned interface with the perovskite absorber. The interaction energy between the Se‐containing SAM and perovskite absorber is the strongest among the series and it reduces the interfacial defect density, in turn leading to an extended charge carrier lifetime. As a result, PSCs incorporating the Se‐containing SAM achieves a PCE of 22.73% and retains ≈96% of their initial efficiency after a maximum power point tracking test of 500 h without encapsulation under ambient conditions. All of the SAMs are then employed in organic solar cells (OSCs). Again, the Se‐containing SAM‐based OSCs demonstrates the highest PCE of 17.9% among the three molecular SAM‐based OSCs. This study demonstrates the great potential for precisely engineered SAMs for use in high‐performance solar cells. [ABSTRACT FROM AUTHOR]

Optical activity (1-3) is the result of chiral molecules interacting differently with left versus right circularly polarized light. Because of this intrinsic link to molecular structure, the determination of optical activity through circular dichroism (CD) spectroscopy has long served as a routine method for obtaining structural information about chemical and biological systems in condensed phases (4-6). A recent development is time-resolved CD spectroscopy, which can in principle map the structural changes associated with biomolecular function (7) and thus lead to mechanistic insights into fundamental biological processes. But implementing time-resolved CD measurements is experimentally challenging because CD is a notoriously weak effect (a factor of [10.sup.-4]-[10.sup.-6] smaller than absorption). In fact, this problem has so far prevented time-resolved vibrational CD experiments. Here we show that vibrational CD spectroscopy with femtosecond time resolution can be realized when using heterodyned spectral interferometry to detect (8-10) the phase and amplitude of the infrared optical activity free-induction-decay field in time (much like in a pulsed NMR experiment). We show that we can detect extremely weak signals in the presence of large achiral background contributions, by simultaneously measuring with a femtosecond laser pulse the vibrational CD and optical rotatory dispersion spectra of dissolved chiral limonene molecules. We have so far only targeted molecules in equilibrium, but it would be straightforward to extend the method for the observation of ultrafast structural changes such as those occurring during protein folding or asymmetric chemical reactions. That is, we should now be in a position to produce 'molecular motion pictures' (11) of fundamental molecular processes from a chiral perspective., CD spectroscopy is considered an incisive tool for determining the secondary structure of proteins in solution (4-6,12,13). But biomolecules participating in chemical or biological reactions often undergo ultrafast structural changes [...]

Li-metal batteries (LMBs) are regarded as next generation storage devices for applications in a wide range of fields, such as electric vehicles and grid-scale energy storage. Unfortunately, their practical applications have been restricted by some defects including safety hazards, low coulombic efficiency (CE), and lithium dendrite growth. Inspired by the low-cost electrolytes in industrial applications, a low concentration bisalt electrolyte (LBE) for practical LMBs is proposed in this work. The synergistic effect of bisalt (0.3 M lithium bis(fluorosulfonyl)imide (LiFSI) and 0.2 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)) and weakly solvating solvent (1,4-dioxane (DX)), provides robust and conductive solid/cathode electrolyte interphase (SEI/CEI) layers on the Li metal anode and LiFePO4 (LFP) cathode, respectively. The majority of salt anions exist in associated states, such as contact ion pairs (CIPs) and aggregates (AGGs), as observed in highly concentrated electrolytes. These ion associates are involved in the formation of stable and LiF-rich SEI and CEI layers which suppress the dendrite growth on the Li anode and prevent parasitic reactions on the LFP cathode. The average CE of the Li‖Cu cells in the LBE was 99.2%. Furthermore, LBE also improved the cycling stability of a Li‖LiFP cell, with a capacity retention of 78.5% after 400 cycles. These results demonstrate the benefits of LBE, paving way for the industrial application of LCE. [ABSTRACT FROM AUTHOR]

Recent advances in perovskite solar cells (PSCs) performance have been closely related to improved interfacial engineering and charge selective contacts. Here, a novel and cost‐competitive phenothiazine based, self‐assembled monolayer (SAM) as a hole‐selective contact for p‐i‐n PSCs is introduced. The molecularly tailored SAM enables an energetically well‐aligned interface with the perovskite absorber, with minimized nonradiative interfacial recombination loss, thus dramatically improving charge extraction/transport and device performance. The resulting PSCs exhibit a power conversion efficiency (PCE) of up to 22.44% (certified 21.81%) with an average fill factor close to 81%, which is among the highest efficiencies reported to date for p‐i‐n PSCs. The new SAM also demonstrates the outstanding operational stability of the PSC, with increasing PCE from 20.3% to 21.8% during continuous maximum power point tracking under a simulated 1 sun illumination for 100 h. The reported findings highlight the great potential of engineered SAMs for the fabrication of stable and high performing PSCs. [ABSTRACT FROM AUTHOR]

Supercapacitors exhibit excellent power density and durability due to their high ionic conductivity and the electrochemical stability of nitrile or carbonate-based electrolytes. However, these commonly used electrolytes have inherent risks due to the high flammability of organic solvents. With the widespread use of supercapacitors, such safety problems have aroused great concerns. Although considerable research efforts have been devoted to improve the safety of lithium-ion batteries, research focusing on safe supercapacitor performance is limited. Here a nonflammable organic electrolyte based on trimethyl phosphate (TMP) solvent is proposed for safe operation. The physical and electrochemical characteristics of the TMP-based electrolyte are investigated by self-extinguishing time, ionic conductivity, viscosity, cyclic voltammetry, and charge–discharge measurements. We demonstrate that the TMP-based electrolyte enables dramatic improvements in safety as well as good transport properties and stable charge–discharge cycling for 10 000 cycles at a high working voltage (3.3 V) at both low and high current densities. The TMP electrolyte was found to decompose and form a film on the electrode surface preventing further electrolyte decomposition. This helps to widen the electrochemical stability window of supercapacitors, realizing high energy and power by increasing the upper voltage. Therefore, the electrolyte system reported here is a promising candidate for safe and performant supercapacitors in large-scale energy storage applications. [ABSTRACT FROM AUTHOR]

Lithium metal batteries (LMBs) have the potential to deliver a greater specific capacity than any commercially used lithium battery. However, excessive dendrite growth and low Coulombic efficiencies (CEs) are major hurdles preventing the commercialization of LMBs. In this study, two different salts, lithium difluorophosphate (LiDFP) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), are chosen for use in concentrated electrolytic systems. By mixing salts with vastly different cation–anion interaction energies, the ion solvation structures in the electrolyte can be modulated to enhance the physical/electrochemical properties and suppress Li dendrite growth in LMBs. Among the investigated electrolyte systems, 2.2 m LiDFP + 1.23 m LiTFSI in 1,2‐dimethoxyethane is proposed as a highly promising electrolyte system because of its high conductivity (6.57 mS cm−1), CE (98.3%), and the formation of an extremely stable solid–electrolyte interface layer. The bisalt electrolyte presented herein, as well as the associated concepts, provide a new avenue toward commercial LMBs. [ABSTRACT FROM AUTHOR]

Ultrafast two-dimensional infrared (2DIR) spectroscopy has been proven to be an exceptionally useful method to study chemical exchange processes between different vibrational chromophores under thermal equilibria. Here, we present experimental results on the thermal equilibrium ion pairing dynamics of Li+ and SCN- ions in N,N-dimethylformamide. Li+ and SCN- ions can form a contact ion pair (CIP). Varying the relative concentration of Li+ in solution, we could control the equilibrium CIP and free SCN- concentrations. Since the CN stretch frequency of Li-SCN CIP is blue-shifted by about 16 cm-1 from that of free SCN- ion, the CN stretch IR spectrum is a doublet. The temperature-dependent IR absorption spectra reveal that the CIP formation is an endothermic (0.57 kJ/mol) process and the CIP state has larger entropy by 3.12 J/(K mol) than the free ion states. Since the two ionic configurations are spectrally distinguishable, this salt solution is ideally suited for nonlinear IR spectroscopic investigations to study ion pair association and dissociation dynamics. Using polarization-controlled IR pump-probe methods, we first measured the lifetimes and orientational relaxation times of these two forms of ionic configurations. The vibrational population relaxation times of both the free ion and CIP are about 32 ps. However, the orientational relaxation time of the CIP, which is ∼47 ps, is significantly longer than that of the free SCN-, which is ∼7.7 ps. This clearly indicates that the effective moment of inertia of the CIP is much larger than that of the free SCN-. Then, using chemical exchange 2DIR spectroscopy and analyzing the diagonal peak and cross-peak amplitude changes with increasing the waiting time, we determined the contact ion pair association and dissociation time constants that are found to be 165 and 190 ps, respectively. The results presented and discussed in this paper are believed to be important, not only because the ion-pairing dynamics is one of the most fundamental physical chemistry problems but also because such molecular ion-ion interactions are of critical importance in understanding Hofmeister effects on protein stability. [ABSTRACT FROM AUTHOR]

The important objective in improving supercapacitor's performance is to increase their operating voltage and expand their working temperature range. Among various organic electrolytes reported so far, the conventional acetonitrile (AN)-based electrolyte features the highest conductivity but suffers from a relatively low operational voltage window (2.5−3.0 V). Our study investigated binary mixtures, combining propionitrile (PN) and AN as the electrolytes designed for high-voltage and high-rate supercapacitors to address this limitation. The physical and electrochemical properties of various binary mixtures are systematically examined. The supercapacitors utilizing these binary electrolyte systems demonstrated remarkable capacitance retention over 10,000 cycles at the upper voltage of 3.4 V, in contrast to the significant capacitance degradation observed in cells using single AN-based electrolytes. Among the various binary electrolytes, carbon-based supercapacitors using a PN−AN with a 20:80 vol ratio achieved an optimal balance among the ionic conductivity (42.2 mS cm−1), long-term stability, working voltage (3.4 V), energy density (32.6 Wh kg−1), and power density (2278 W kg−1). Impressively, it also obtains good rate capability and capacitance retention (>95 %) at a voltage as high as 3.4 V under ultra-low temperature of −40 °C. This approach paves the way to developing high-voltage supercapacitors with optimal performance. [Display omitted] • Binary electrolytes of AN and PN are optimized. • The PA-28 electrolyte represents the optimal compromise. • Supercapacitors based on PA-28 electrolyte can work at 3.4 V and −40 °C. [ABSTRACT FROM AUTHOR]

4-Azidoproline (Azp) can tune the stability of the polyproline II (PII) conformation in collagen. The azido group in the 4Rand 4Sconfigurations stabilizes and destabilizes the PIIconformation, respectively. To obtain insights into the dependence of the conformational stability on the azido configuration, we carried out Fourier transform (FT) IR experiments with four 4-azidoproline derivatives, Ac-(4R/S)-Azp-(NH/O)Me. We found that the amide I and azido IR spectra are different depending on the azido configuration and C-terminal structure. The origin of such spectral differences between 4Rand 4Sconfigurations and between C-terminal methylamide and ester ends was elucidated by quantum chemistry calculations in combination with 1H NMR and time- and frequency-resolved IR pump–probe spectroscopy. We found that the azido configurations and C-terminal structures affect intramolecular interactions, which are responsible for the ensuing conformational and thereby IR spectral differences. Consequently, 4-azidoproline conformations modulated by azido configurations can be probed by IR spectroscopy. These findings suggest that 4-azidoproline can be both a structure-control and -probing element, which enables the infrared tracking of proline roles in protein structure, function, and dynamics. [ABSTRACT FROM AUTHOR]

Despite prolonged scientific efforts to elucidate the intrinsic peptide backbone preferences of amino-acids based on understanding of intermolecular forces, many open questions remain, particularly concerning neighboring peptide interaction effects on the backbone conformational distribution of short peptides and unfolded proteins. Here, we show that spectroscopic studies of a complete library of 400 dipeptides reveal that, irrespective of side-chain properties, the backbone conformation distribution is narrow and they adopt polyproline II and β-strand, indicating the importance of backbone peptide solvation and electronic effects. By directly comparing the dipeptide circular dichroism and NMR results with those of unfolded proteins, the comprehensive dipeptides form a complete set of structural motifs of unfolded proteins. We thus anticipate that the present dipeptide library with spectroscopic data can serve as a useful database for understanding the nature of unfolded protein structures and for further refinements of molecular mechanical parameters. Proteins 2011; © 2011 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) optical spectroscopy based on stimulated photon echo geometry requires multiple ultrashort pulses of which spatiotemporal properties and optical phases can be precisely controlled. Also, it is possible to change the incident beam polarization directions defined in a laboratory frame. Here, we introduce the polarization-angle-scanning (PAS) 2D spectroscopy and show that the diagonal and cross-peak amplitudes in the 2D spectrum can be arbitrarily modulated by spatially controlling the beam polarization directions. For a coupled anharmonic oscillator system, we specifically demonstrate that either diagonal or cross-peaks in the measured 2DIR spectra can be selectively eliminated and show that such polarization angles provide direct information on the relative angles between coupled transition dipoles and thereby on intricate details of molecular structures. We thus anticipate that the present PAS 2D optical spectroscopy can be a useful experimental method enabling us to probe structural evolutions of nonequilibrium state molecules by monitoring the time-dependent changes of the relative transition dipole directions. [ABSTRACT FROM AUTHOR]