The structure and composition of lithium ion solvation spheres of electrolyte solutions composed of common lithium salts (LiTFSI, LiPF6, LiBF4, and LiClO4) dissolved in aprotic polar linear and cyclic carbonate solvents (propylene carbonate (PC) or dimethyl carbonate (DMC)) have been investigated via a combination of FTIR, 13C NMR spectroscopy, and density functional theory (DFT). Results from the two different spectroscopic methods are in strong agreement with each other and with predictions from quantum chemistry calculations. The coordination of the carbonyl oxygen of the solvents to the lithium cation is observed by IR spectroscopy. The ratio of coordinated to uncoordinated PC and DMC has been used to determine solvent coordination numbers which range from 2 to 5 depending on salt, solvent, and concentration. The relative stability of the lithium–anion solvates were examined using DFT employing the cluster-continuum approach including changes to the intensity and frequency of the IR bands along with the populations of the cis–cis and cis–trans conformers of DMC in the lithium ion solvation shell. Solvent coordination is dependent upon the nature of the salt. Weakly associating salts, LiTFSI, LiPF6, and LiClO4, dissociate to a similar degree with LiPF6 being the most dissociated, while LiBF4 had significantly less dissociation in both solvents. This investigation provides significant insight into the solution structure of commonly used LIB electrolytes over a wide range of salt concentrations.

Silicon electrodes were cycled with electrolytes containing different salts to investigate the effect of salt on the electrochemical performance and SEI structure. Comparable capacity retention were observed for the 1.2 M LiPF 6 , LiTFSI and LiClO 4 electrolytes in ethylene carbonate (EC):dimethyl carbonate (DEC), 1:1, but severe fading was observed for the 1.2 M LiBF 4 electrolyte. The differential capacity plots and EIS analysis reveals that failure of the 1.2 M LiBF 4 electrolyte is attributed to large surface resistance and increasing polarization upon cycling. However, when LiBF 4 was added as an electrolyte additive (10% LiBF 4 and 90% LiPF 6 ), the capacity retention and Coulombic efficiency were improved. The SEI was analyzed by FTIR and XPS for each electrolyte. Both spectroscopic methods suggest that the main components of the SEI are lithium ethylene dicarbonate (LEDC) and Li 2 CO 3 in the 1.2 M LiPF 6 , LiTFSI and LiClO 4 electrolytes, while an inorganic-rich SEI, composed of LiF and borates, was generated for both the Silicon negative electrodes for lithium ion batteries have attracted academic and industrial interest, since they provide ∼10 times more specific capacity (3579 mA g −1 ) than graphite (372 mA g −1 ). However, the large volumetric changes during lithiation and delithiation limits commercial application.1 The volume changes result in mechanical stress to individual Si particles and the binder which maintains physical contact between electrode components, thus degenerating the electrode laminate upon repeated lithiation/delithiation. 2,3In particular, it has been demonstrated that the electric contact loss becomes severe during delithiation when the Si particles are contracted. Thus, incomplete delithiation due to contact resistance has been reported as one of dominant failure mechanisms. [4][5][6][7] In addition to the volume contraction, the solid electrolyte interphase (SEI) has been reported to be another factor that impedes the reversibility of lithiation. 5,7 When the SEI on silicon is modified by fluoroethylene carbonate (FEC), the capacity retention, reversibility of lithiation, and suppression of electrolyte decomposition are observed. 5,7,8 Since the improvement of the SEI is critical for improving the electrochemical performance of Si electrodes, great efforts have been devoted to modify the SEI by using electrolyte additives, surface coatings, or concentrated electrolytes. [9][10][11][12][13][14][15][16] Recently, it has been reported that the SEI can be significantly modified by changing the electrolyte concentration. [16][17][18] For instance, propylene carbonate (PC)-based electrolytes do not generate a stable passivation layer on graphite at low salt concentration. However, upon dissolving high concentrations of either LiPF 6 or LiTFSI into PC a LiF rich passivation layer is generated on graphite affording electrochemical reversibility of the graphite. 16,18 The change in salt concentration has been reported to result in a change solution structure of the electrolyte. 16,...

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A predictive film thickness model based on an accepted equation of state is applied to the spin-coating of sub-micron poly(methylmethacrylate) viscous thin films from toluene. Concentration effects on density and dynamic viscosity of the spin-coating solution are closely examined. The film thickness model is calibrated with a system-specific film drying rate and was observed to scale with the square root of spin speed. Process mapping is used to generate a three-dimensional design space for the control of film thickness.

The morphology of sub-micron poly(methyl methacrylate) films coated to glass supports by spin coating from toluene is examined using surface profilometry. Wrinkled surfaces with local quasi-sinusoidal periodicity were seen on the surfaces of films with thicknesses of larger than 75 nm. The surface wrinkles had large aspect ratios with wavelengths in the tens of microns and amplitudes in the tens of nanometers. Wrinkles that formed during spin-coating are attributed to surface perturbations caused by Rayleigh–Bénard–Marangoni convective instabilities. The effects of film thickness, coating solution concentration, and drying rate on the thin film surface morphology are investigated. The results can be used to prepare surfaces with controlled morphology, either smooth or with periodic wrinkles.

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Leaf senescence involves lipid droplet (LD) degradation that produces toxic fatty acids, but little is known about how the toxic metabolites are isolated from the rest of the cellular components. Our ultramicroscopic characterization of cytosolic LD degradation in central vacuole-absent cells and central vacuole-containing cells of senescent watermelon leaves demonstrated two degradation pathways: the small vacuole-associated pathway and the central vacuole-associated pathway. This provided an insight into the subcellular mechanisms for the isolation of the fatty acids derived from LDs. The central vacuole-containing cells, including mesophyll cells and vascular parenchyma cells, adopted the central vacuole-associated pathway, indicated by the presence of LDs in the central vacuole, which is believed to play a crucial role in scavenging toxic metabolites. The central vacuole-absent intermediary cells, where senescence caused the occurrence of numerous small vacuoles, adopted the small vacuole-associated pathway, evidenced by the occurrence of LDs in the small vacuoles. The assembly of organelles, including LDs, small vacuoles, mitochondria and peroxisome-like organelles, occurred in the central vacuole-absent intermediary cell in response to leaf senescence.

The absorbance, excitation, and emission spectra of ultra-thin films of rhodamine 6G (Rh6G) spin-cast on poly(methylmethacrylate) (PMMA)-coated glass slides are examined as a function of both PMMA and Rh6G thickness. The thickness of PMMA has a little effect on the absorption or emission properties of Rh6G. At low surface coverage, the spectral properties of Rh6G are dominated by isolated molecules. As the Rh6G thickness increases, there is no evidence for exciton formation. Instead, the Rh6G molecules aggregate, which is responsible for the observed absorption and emission spectra. The aggregates significantly quench the emission so that the maximum emission intensity is found just below a monolayer surface coverage. The lack of exciton formation, which is unexpected, is attributed to the surface morphology of PMMA, which has a periodic surface structure.